There are already many great modding guides available scattered about the Internet, so I’m not going to try to make an attempt at a comprehensive guide. These are the basics along with some of my own recommendations on the process.
To my knowledge, the most common alternative to manual installation (see the section below) is CKAN (The Comprehensive Kerbal Archive Network). It presents you with a list of many mods (not all mods, and not necessarily the most up-to-date mods, but many of them). You then select the ones you want to install (it’ll give you some information about relationships, contents, versioning etc.) and install them – CKAN takes care of pulling down and installing any necessary mods alongside the ones you’ve selected, as well as recommending frequently-paired mods.
By many measures it’s a useful tool and it gets you using mods quickly. I would probably recommend this method to a beginner, but if you get the modding bug, you’ll soon bump up against its limitations (some of which I allude to below).
Installing mods manually in KSP is simple. I prefer to do it manually for a few reasons:
- Not all mods are available through alternative methods; all mods can be installed manually.
- Alternatives such as CKAN (see the ‘Automatic’ section below) don’t have their repositories updated as often as I’d like.
- Alternatives such as CKAN don’t easily let you “break the rules” and install ostensibly-incompatible mods to your current KSP version.
- Installing manually slows the pace a little and helps me think about and fix potential incompatibilities.
- Installing manually makes me get used to the way KSP loads game files, helping solve incompatibilities that might arise further down the line.
When you download them from the links on this page (and elsewhere on the Internet), they generally come in .zip files. Extract the .zip file into your GameData folder found at the top-level of your KSP installation directory. So you’ll have something like this:
<KSP Installation Location>\GameData\ModName
KSP then does the hard work in actually making sense of what’s in that folder. If you install through Steam onto your C-drive on Windows (arguably the most common setup), your full path would be:
C:\Program Files (x86)\Steam\steamapps\common\Kerbal Space Program\GameData\ModName
Where to find mods to install manually
If you’re used to using CKAN, all the mods are ready and waiting in a neat list. You don’t need to think about where to get them. If you’re installing manually, you need to go and look for the file(s) yourself. Google is your friend.
Mods generally have a dedicated thread on the Kerbal Space Program forum. The modders are overwhelmingly helpful and they’ll give information about any special installation procedures, known incompatibilities, recommended mods to go with theirs etc. The modders are generally happy to respond to sensible bug requests or help work out incompatibilities. Just make sure you have a good comb of the last dozen or so pages before asking for help – your efforts will be appreciated!
There’s also a good repository on Curse. I almost exclusively use the KSP forum, though.
Keep a Backup!
I learned this the hard way. The last thing you want is to tweak and perfect your mod setup to have Steam auto-update your KSP installation so that a smattering of mods are no longer compatible. Ugh.
So I have side-by-side installations. I just copy the default KSP directory to a second folder at the same level e.g. “_Kerbal Space Program_working” (prepending the underscore ensures it appears at the top of the folder view). So I have two installations of KSP:
/_Kerbal Space Program_working /Kerbal Space Program
The latter updates with Steam (and I can always jump in and play up-to-date vanilla, if I feel like it), and the former stays constant save for my own tinkering.
Add One Mod at a Time
This can be very tedious, but it’s worth it. It’s quicker to add one mod at a time and test that everything seems to be OK before adding the next than it is to add dozens of mods and have to guess at what broke or what’s incompatible. At least, it is if you don’t know much about how the mods work.
If you’re feeling brave, you can add batches of mods at once. I would do this with mods that seem to be unrelated e.g. a mod that adds extra contracts and a mod that makes visual changes. This way you minimise the chance of conflict between mods in the same batch (generally the cause of trouble).
Before you add another mod, or mods, to a working loadout, take a screenshot of your GameData folder or write down all the mods that you use. If you want to go further, record the versions you’re using. You can get an automatically-generated list when KSP is loading by using KSP-AVC (Add-On Version Checker).
This is something that I always forget to do but always wish I’d done when I break things. It can be all too easy to accidentally delete folders, move mods into other mod folders, or forget what mods you added when adding them in batches. It makes debugging that much harder.
The alternative is to make a back-up of the whole GameData folder before doing anything, which is fine if you have ample storage.