1. Find out what the SW needs (external libs, special features
of the OS, HW).
2. Find out what compiler was used, and if it is compatible with
anything on the Amiga.
3. Rewrite all parts that you found in 1, or rewrite the SW in
a way that these aren't needed any more.
4. Push the whole mess through the compiler.
5. Start from 1. as the first try didn't produce a working binary :-o