Assuming you're running Windows here, since you didn't tell me your platform:
Install python 3. Clone the repo/download the zip/whatever. Place clean FR rom (test.gba) in the same directory as this. Hold shift and right click the directory. Choose "open in command prompt" or similar. If you cannot see this, open a command prompt window and enter 'cd C:/Path/to/folder/you/downloaded'. Then type 'assemble.py' and hit enter. If you see no errors then it worked. Test it in game using the "copy player" behaviour. P.S. your profile font is awful and I can barely read it :(