Hello Lolamaras! "Welcome to SubSim!"
Look in the folder where you have SH4 installed, and consult and / or print-out the "SH4_Q-Ref_Card_Back.jpg" and "SH4_Q-Ref_Card_Front.jpg" images, which are the keyboard short-cuts for the game. The Function keys up top are shortcuts to rooms (usually), the number keys below that are the speed keys, and then various letter keys are for "commands".