for normal users, only these parts are necessary:
1)Download and install Tortoise SVN if you don't already have it (
http://tortoisesvn.net/downloads.html)
2) Prepare a folder to contain your copy of the project
Create an empty directory that will hold your working copy (i.e. - local directory on your machine which will be your 'image' of the central repository - this is where you will make your changes when you want to contribute them and where other people's changes will sync down to). I strongly recommend that this is NOT your 'live' copy in 'program files/firaxis/...'. Mine is in \development\C2C, but the location doesn't matter - just put it somewhere convenient where you have space.
3) Checkout from the repository to the folder you created in (2). This will get the current revision and make a permanent connection between your working folder and the repository. Assuming you have installed SVN as in (1) you can do this by right-clicking the directory in Windows Explorer and selecting 'Tortoise SVN/Checkout...'. When it asks you for the repository URL enter 'svn://svn.code.sf.net/p/caveman2cosmos/code/trunk'. It's 3.4G (uncompressed transfer I'm afraid), so obviously this will take a while (might want to do it overnight - the upload took me about 8 hours!). Future refreshes or uploads (aka Commits) only get changed files, so they will be much, much faster, especially since the really big things like art assets and movies don't tend to change much.
4) After it's all copied you are up and running!
B: Getting the current version into play:
1) Create an empty folder somewhere not inside 'program files'
2) Right click and drag the root folder of your working copy to this new folder
3) Select the 'export without versioned files' option
4) Move the result into your mods folder (and rename it from C2C to Caveman2Cosmos)
Alternative from Dusckr87
This is what I do for every mod I "do" svn:
1. Create a "temp" folder.
2. Right click on an empty spot in the temp folder, choose SVN checkout, connect to the repository, download the mod.
3. Extract the entire folder to a second temp folder, copy that folder to the BTS\mods folder, and zip the mod. This step is of course optional.
4. When I update, I update the first folder only (by right clicking and choosing "update SVN", not "SVN checkout"). When I want to play that update, I repeat step 3, and delete the "working" folder in the BTS folder and replace it with the new mod.
5. Never update your folder in the BTS folder, and always delete that folder before replacing with the update.