An inset frame is made for a canvas board about 3mm thick. The board goes into the front of the frame, with no glazing in front of it.
Step 1: check the fitting kit
Open your fitting kit. In it you should find Velcro dots, D-rings and screws, and picture cord, in quantities to suit the size of your inset frame. (The foam pads in this picture are supplied only with canvas floater frames.)
Step 2: add the Velcro dots
Turn your board or MDF panel face down. Stick a Velcro dot near each corner and, on a bigger board, more dots spaced evenly along the edges. Then press the other half of each dot onto the ones on the board, leaving the sticky side up. These hold the board in place in the frame.
Step 3: fit the board and fixtures
Place the board into the front of the frame, then press down gently on each corner and along the edges where the Velcro dots are, so that they stick.
Then turn the frame over and fit the hanging fixtures. Screw a D-ring into the back of the frame on each side, about a third of the way down, and tie the cord between them. Your frame is ready to hang.