This YouTube video might help to understand.The "front plate" in front of the "dial" goes outside the dashboard
and, the radio goes behind the dashboard
and, the two radio posts go through the holes in the dashboard
A washer and nut goes around each post; and, the knobs get pushed onto the posts.
If the knobs are loose on the posts, the post ends can be carefully/slightly opened.
If this is incorrect or this is not clear, maybe someone will correct or add information/instructions.
I'll see if I can find the original installation instruction.