What Midi Files Can I Use?

Any standard midi file will do. Transupposer only reads note on, note off and program change messages so Type 0 and Type 1 files are both valid.

How Can I Use My Transposed Midi?

Most software that supports midi files will have an option to import from Midi. Muse Score allows you to open midi files like you would open a standard Muse Score Project

How Can I Generate My Input Midi?

Any good composition software should have an export to Midi function, so whatever you use to compose you should search its user manual for this option. In Muse Score this option is Located at File/Export and you should select Standard Midi File (*.mid) as the file type.