Measure the length of the edge that you need to install the transition bar to and cut the bar to that length with a hacksaw.
Screw the transition bar to the concrete with masonry screws, using a hammer drill to install the screws. Place the bar underneath the edge of the carpet.
Cut the edge of the carpet with a utility knife so that it's about a 1/4-inch away from the transition bar.
Stretch the carpet into the transition bar at the corner with a knee-kicker and then tuck the edge of the carpet into the bar and onto the pins inside it with a stair chisel.
Place a wooden block on top of the bar and tap it down with a hammer to bend the flange down on top of the carpet.