I could possibly have recorded a step-by-step howto on preparing the mineyourmind launcher on windows, but the kid (KidC, 6 years) is hogging the PC. If you've got one instance working, I think we'll leave it at that.
I uploaded the files here: GitHub - MyM-ModpackTeam/AgrarianSkies-Plus Just create a 1.6.4 instance with forge in MultiMC and drop the files in there.