Sorry I don't have time explain to you how to calculate different parts of solution, but:
Often you have to get yourself ready to shoot maybe just in few minutes. So there is not time to calculate but you have to use your eyes and "nose". You could try this with a single mission:
Just raise the scope and choose your target. First time, don't try to shoot more than one target at time. Have a look, and ESTIMATE Ab (AOB, Angle of bow) and targets speed. Because you won't be sure how fast target is moving ahead, your estimate could be something like "It's making 6 - 8 knots..." So, now you can use 7 knots in TDC (input manually, count those little "clicks" you can hear when moving the needle). Because this is your first time, use salvo of 3 torpedoes and note 5 degrees spread angle is often too much - you could use maybe just 1 or 2 degrees.
When estimating Ab you should remember the bigger the Ab is more likely you will estimate it to be bigger than it is. Ab 30 degrees+ is hard to see accurately but it's skippers one important ability to get this information just by using his eyes.
Range you allready know how to get.
When using notepad, be sure values are going into TDC. Only speed is not shown in notepad if you input it manually.
It's not that hard really. I do plotting usually only in night attacks. Daytime if I'm in good postition to get them submerged without need to travel ahead, I usually dive without any plotting but using just normal approach tactics and my eyes and experience.
Good luck, rob! Have fun!
-RC-