1. Import the OBJ file into Autodesk Remake. Remake is made for editing scans and other similar files.
2. Next we need to edit the file down to just what we need to do this use the Selection tool and then right click and select Delete. Next we need to fill in all the holes, which you can use the Fill Holes tool for.
3. After that we need to decimate the file to less than 30,000 triangles (or decimate it to less than 10,000 if you are doing this on a laptop). This is for performance reasons after you get into Fusion 360.
4. Export as a OBJ file for Fusion 360.
5. Import to Fusion 360, using Insert Mesh
6. Next, Right click on the mesh, and click convert to B-REP
Now you have a Fusion 360 model which you can edit and mill on the Othermill. To read one way I've used this process in my own work, please visit my blog post: 3D Scan to Chocolate in 48 Hours.