Hi @Xevoe, welcome to the forum 
We don’t currently have any examples for controlling thrusters directly with a Raspberry Pi.
If you’re just starting out with programming and Raspberry Pi, you may want to use the Thonny IDE. You’ll likely need to learn how to install and import libraries, and some basic Python syntax, before you’re able to continue.
Assuming you have a BasicESC for controlling your thruster, you can send that commands using a servo-style PWM signal. It may be helpful to search for “raspberry pi control servo Python tutorial”, but because our ESCs have quite precise timing requirements
If key press control is important to you, you’ll need to look for libraries that support doing that. pynput supports listening to keyboard events, so could be a good option (assuming it works on Raspberry Pi). If you don’t need frequent speed changes it may be simpler to create a program that reads repeated input from the user, and allows that to specify the speed / the PWM pulse-duration.
If you’re not interested in programming, and just want to control a servo signal with a Raspberry Pi, we will at some point create a BlueOS Extension that allows doing so, but there’s no timeline on that - it could even be some time next year.