1. Download the STEP files for the motor.

    1. https://www.pololu.com/file/0J1868/37d-gearmotor-3d-models.zip

    2. Un-zip the file 37d-gearmotor-19-30-encoder.step

  2. In Fusion 360, click File > Open, in the prompt click "Open from my computer…​"

  3. Select the STEP file that you saved earlier.

  4. The model will be opened, save the model so it can be used with Fusion 360.

  5. Create a new file for the assembly.

  6. Assemble the motor and the motor mount together.

How the assembly should look:

motor assembly

Below is a video guide on how assemblies work:

https://www.youtube.com/watch?v=O1p7Sn1eMmE