The steps for installation and set up for using the SVN is in the Opening Post for the SVN thread right here in this section. The SVN does not provide a link for a particular version. ALL versions are available by using the Export function of the SVN. The Point of the SVN usage is to keep your C2C mod updated to the current level of development And Bug fixes.
No need to keep re-downloading from Moddb, or re-installing Civ IV BtS. And since you got your copy from Steam they have a more convoluted path than non steam.
There are many Steam users here who can chime in with where the Mod needs to be in the right path (I don't use steam so i can't help with that). Just don't put the Mod into the My Documents BtS Mods folder.
And as for the Admin rights, not only Civ IV BtS needs you to do it but also the Caveman2Cosmos Mod needs to be set to admin, especially with Steam.
1 last item, do you have another possibly older version of C2C in your BtS/Mods Directory? And if you do/did, hopefully you did not try to overwrite it with the MODDB D/L. Always remove older versions out of the Civ IV\BtS path before putting in a newer version.
JosEPh