The more recent versions of the software don't have a provision for a "new" satellite. The version that came with mine did, but I updated and lost that.
So you will have to use a satellite you don't intend to program... such as a c-band or one over Brazil, etc.
Rename that satellite, delete all the TPs for that satellite, and add the TPs for I-8.
That's how I did it, I used PAS1R, since it's highly unlikely I would ever want to program in that satellite. If you're using USALS you would also have to change the location to 89W.