IF you decide to add GWX 2/2.1/3 to your gaming experience please know that sub school becomes very difficult - don't get upset and throw in the towel.
Start with the "practice" exercises first to get your feet wet prior to taking each exam. Don't rush through sub school. One mission is designed to teach you how to set a plotted course - tools along the top of the screen upper right - map is available by hitting F5. Take your time piloting the ship, making necessary corrections and getting used to the various key controls through the first mission. It's very straight forward but you can learn a ton from what is presented.
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As to torpedoes, get used to using F3 to go to the attack periscope - and you can hit TAB to zoom in. One thing to keep in mind - IF a ship is further away than 10,000 yards and your zoomed to 10X, you may barely see it at that distance. Don't immediately lock onto the closest 500 meter ship - look to it's left, and further away will be a larger merchant.
This exercise was created to help you understand attacking and moving to get best positional range. Yes, you can sit and just turn the ship, but it's best to start learning how to move and attack - otherwise known as Tactical Strategy.
Yes, you can keep doing automatic targeting, which makes the game easier - BUT there is a true challenge waiting for you in SH3 - manual targeting. Talk about fun, *woot*
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The flak missions against air targets will test you, and don't be surprised if you fail the first time. Plotting a course quickly is key here, along with getting crewmen to the flak gun once you decide to attack - if you survive that long.
It will also teach you damage control, knowing how to effect repairs on your ship will be key here.
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Lastly, is what I like to call the
Kobayashi Maru experience. Exam 4 will put you into direct combat against a convoy, but they will fight back - be prepared to have your eyes opened the first time death from above reigns down in the form of destroyers.
Good luck and welcome to Subsim...