Welcome aboard mate.
To find your sub just hold control and right click the mouse. The sub marker will be under the arrow. Set Speed on the telegraph dial ( the first of three lower right) Set course by clicking the compass. Set depth on the last dial.
There are gray tabs under the dials that will change the scale for each.
The F1 key will give you all the the keyboard commands.
You do most of your work on the Navigation map, so start there and just click all the buttons to see what they do, you can't hurt anything. The third button in will mark way points for navigation. That is the main tool for getting from one place to another.
Check out this link:
http://www.subsim.com/radioroom/showthread.php?t=146795
Play on easy mode till you get a feel for things, than you can step up the difficulty.
Just keep trying things and reading the form and you will soon get the hang of it. It is well worth the effort, believe me.
As you can see there are a lot of helpful captains here so ask away and we will try to help.
Magic