And how do I check the idle speed? Feel free to just tell me to search the forums if there are posts about it already
You can adjust the idle by looking at the video that Chris-G5 has mentioned.
It takes 1/4 to 1/2 turn only. You need a long flat and wide screw driver to reach the brass screw.
One hint -
Before turning the screw, mark with a blue marker the position of Brass Screw Slot relative to the surrounding wall, so that you can visually see how much you turn it.
You do not need to buy a tachometer for this. Just listen to the sound and you will be able to pick up the change in idle speed. Or you can compare the sound on the video to your bike idle.