I want to download the one that is compatible with the 4 gig enabler

You'll still need the files from the normal version of NVSE so don't uninstall anything. Go to the http://nvse.silverlock.org/page, scroll down the Troubleshooting area and look for the download link for the alternate loader. Once you have that and put the proper files where they need to go just use fnv4gb.exe to start the game with NVSE.