So go into Settings —> Game controller —> It should be in the left menu, press the arrow in between the two boxes which will get it into the right menu. Afterwards press on the name of your wheel and select AutoConfig, then follow the instructions
You're going to really struggle to play OMSI on a 180 degree wheel like that - those wheels are fine for racing games where you only need to turn the wheel about 180 degrees to have full control over the car, but a bus steering wheel tends to rotate approximately ten times that amount. That means for every one degree you turn your steering wheel, you'll turn the steering wheel in game by ten degrees, which will make the bus really hard to control. 900 degrees is basically the minimum for usability, though it's still not ideal.
You might be able to make it just about usable by setting it up with a high degree of non-linearity,
Also, you need to be patient in the controller menu, it takes OMSI a long time to load the button and axis list for each controller, and while it's doing that it freezes. Just leave it and wait.