Go to the link given here in this thread :
http://buzz.kickedbyconsole.net/index.p ... 0Drumkits/Download drumkits from here.
Put the drumkit file where you want (I put it in generator folder but it can be anywhere on your hard drive I think).
Put a PsiDrum2 in machine view (and of course connect to the Master).
Right-click on it and load a drumkit.
Go to pattern view and choose the class of drums. Just click on the third column in pattern view. Here you choose the "class" of drum.
01 is Base a.k.a bassdrum generaly, 02 is snare, 02 hihat and so on. It can be different for some drumkits, depending on how the author made it.
Fourth column is for which sample you choose in the class. You can have more than one sample of each drum part (like 5 different kick, 5 different snares, etc).
And at last the fifth column is for trigger the sample.
Notice that PsiDrum 2 can be buggy sometimes. Use instead BTDSYS samplegrid, it can load drumkit. It work a little bit differently. I can explain if you're interested.
Also you have a little tool called drumkit manager that let you create your own drumkit, modify an existing one or export the wav from within a drumkit.
Check this thread to get drumkit manager :
viewtopic.php?f=2&t=2201&p=11522&hilit=drumkit#p11522