Please report to WernerSobe's Advanced School for Submarine Attack Tactics for great, non-muffled movies that will teach you exactly what you want to know.
http://www.subsim.com/radioroom/showthread.php?t=118923.
While you're at it you can look toward the end of the thread for my tutorial on the Dick O'Kane attack method, which doesn't use the PK at all and uses a fixed AoB since you are attacking at 90º to the target track. Not only will you hit the target with this technique, but you will individually aim each torpedo for a specific spot on the target to distribute damage for efficient sinking. Let us know how you do and we'll fill in the blanks!
If you want to use the PK, turn it on first. Then enter target speed, AoB or course (you can see how to forget all about AoB and just use the target's course in Werner's videos), and lastly bearing/range. Then assuming all your parameters reflect reality, you'll hit your target. The important thing is to enter range/bearing LAST. The PK works like a spreadsheet, new data simply replaces old data.