Ok, so you've got the dismount foot inside the barrel. That needs to be outside the wheel rim. So you break the bead, clamp the wheel, then lock the dismount foot against the outside of the wheel rim (yellow arrow, the rim sits inside the "gap")
Place your tyre lever against the "step" on the end of the dismount foot (pink arrow) and lever the bead up and over it, keep the lever in place flat down against the face of the wheel. When you rotate the wheel the lever will slip off the step and stay in place in the wheel (keep holding it) while the dismount foot pulls the tyre bead off the wheel.
Once the top bead's off, lift the tyre so the part closest to you sits inside the stepped middle of the wheel barrel, and do the same action with the tyre lever, on the step of the dismount foot and "hook" the bead over. Then rotate, keeping the lever in place as you did before and the dismount foot will pull it off the wheel.