[XenonSurf]

You steer your sub manually :

- Manually with WASD keys to use the planes for steering and changing depth,
- X to level all out at any moment
- E,C to use ballasts to surface / dive (independent of planes)
- Q,Z to increase / decrease speed.

Using planes and ballasts at the same time will more quickly surface/dive your sub, also depending on speed.

Or:
Give your crew direct orders via the menu for speed, course, depth:

Use mini-bar to set speed, depth.
To set course, press H and move the mouse on the tactical map, right-click to set new course. The sub crew will care about the necessary manoeuvres for you.
X to level all out at any moment

Important:
Use the manual method in combat for torpedo evasion etc.

Hope this helps, no need to longely search for a video, this is so basic that no video will expressely show it to you.