You will want to hook into an appropriate place in the ACD handlers to initiate your process. I put my code in CustomAcdProcessCall_AlertSuccessful, but YMMV.
You will then use the "Create PA Data" toolstep (I pass in the output of UniqueID as the PADataName to guarantee no collisions). Use a "Put PA Data Element" toolstep to add as many variables as you want. For example: if you have a variable in IPA named Process.String1, passing "String1" in as the Element Name will make Process.String1 get whatever you put in the value field.
Then, use "Get Process Properties" to get the Process ID and finally, "Initiate Process" using the Process ID, and the PAData Name - make sure you have something in there for the Initiator Name, but it probably won't get used, so pass in the user id of the person that it should be assigned to as one of the variables as well.
If you do this right, the Process should alert immediately after the call is picked up.