Tutorial for Snap buttons
Make suitable holes for the buttons. The over (female) button may need a slightly larger hole than its counterpart
Match the buttons front and backpieces for over and under button along with the tools.
Under button should fit in to the hole of the tool
The tool should fit into the over button. Make sure that the button snaps on correctly, and note that the tools counterpart is now flipped with the straight side down.
A couple of taps with a hammer should do, no brute force needed.