If you can see blades for the backplate, your backplate may be missing...
The YouTube videos I've seen for 116 cameras had the film loaded centered (and the 3D printed adapters for sale on eBay are made for that position), and advance was by "count the turns" -- which won't be accurate if you use just backing paper, because it doesn't build diameter at the right rate. I recently found that I can cut a strip of backing to the same length as the film from 120 and roll it into the backing and it comes out the same thickness as a new roll, so I'd recommend doing the same. Then, of course, you need to black out the red window. You can also use the "dummy roll" made this way to get the correct turn count for "load by the arrows" roll starting.
A frame mask is optional; if you're going to shoot 120 regularly, you may want to make one, perhaps even move the framing window to the 6x6 track (and wind to even numbers as with a 6x12 format).