When I download a step file it will not open . Directs me to the App store for a programme.

As above

2 Answers

dont try to open it from the folder browser directly, open your CAD program first and then try to open it from there.

To open STEP files in Fusion 360 specifically, go to File > Upload. Drag or select the STEP file you downloaded.

You cannot use Fusion to open STEP files directly from File Explorer, you need to use the above method.