Migrating iTunes to new computer - setup woes...

I have iTunes set up on my Mac Mini, with the music files on an external disk, My Passport. I'm trying to set up all this on a Mac Pro. I've copied all the music files onto a similar external disk My Passport 2. I've gone into preferences and made that the location for the music files.

What I can't do is get the playists to function, though I've copied them onto the hard disc of the Mac Pro. The usual "transfer library" instructions don't work for the Mac Pro, since it has a 250GB startup SSD plus the hard drive, and as said the music files will be on the external drive MyPassport2.

How do I do this? I'm completely stumped.... come to a dead end and need help!!

 

Update - this took an hour with an Apple technician. Unbelievably complicated. Nice guy, though.