First(unless you already have it), you will need to download Tribes 2, then apply the multiplayer patch over that; both can be found HERE. It is preferred that you install to a similar location such as "C:\Dynamix\Tribes 2\" .
You'll also need to go get Tortoise SVN, which we use for easy version/source control over the ironsphererpg project. You can get that HERE. (be sure to get 32bit or 64bit depending on what your system is, you can find out by pressing WindowsKey+Pause/Break while on the desktop.) Also, make sure to install "command line client tools". Tortoise SVN may ask you to restart your system, as it integrates into the Windows Context Menu.
Once both Tribes 2 and Tortoise SVN are installed, create a new folder in "C:\Dynamix\Tribes 2\GameData\" called "ironsphererpg" (see picture).
Once the folder is created, right click it and select "SVN Checkout", and put "https://ironsphererpg.svn.sourceforge.net/svnroot/ironsphererpg" into the "URL of repository" field. (see picture)
Click OK, and the mod will start downloading.
You're almost done, You just need to download the launchers for the mod. You can find them HERE. All you need to do is extract them to "C:\Dynamix\Tribes 2\GameData\" (or similar, just needs to be alongside ispawn.exe and tribes2.exe)
The three launchers that have "Dev" on the end currently don't do much more besides not auto-updating- which the three other launchers do.