If you are working with Notation Composer or Notation Musician, you can use the search function to find MIDI files on line. Once you've located MIDI files of the song you want to translate, convert the MIDI file to a written score in the "Options" menu.
If you are not fortunate enough to have MIDINotate, you can download a trial version or you can transcribe it manually.
For manual translation, try Sebelius for notation and one of the many software packages for slowing music down. Demo versions are available for most.
Start with the easy part. Find the solo or the refrain, and transcribe that first. Solos can be easy because there is basically only one instrument to deal with. The refrain is also a good place to start because its easy to pick out the melody. Starting with the refrain knocks out a lot of work at once.
Once you've got your score written, play back the MIDI version and compare it with the CD version. The more you listen to it, the more likely you are to get it right.