Assuming the follower is assembled to the magazine spring, proceed as follows:
1) Hold the magazine in your left hand, vertically with the bottom up, rear of the magazine toward you;
2) Holding the follower above the opening at the bottom of the magazine, spring straight up;
3) Rotate the follower approximately 60 degrees to the right pivoting the right front corner of the follower (as you are looking at it) in the right front corner of the magazine;
4) Roll (tilt) the follower slightly to the right side and hook the right front corner of the follower (the rounded part) under the right front base plate retaining tab;
5) Tilt the follower back to the vertical. The left front corner of the follower should fit easily behind the first groove in the left side of the magazine;
6) Again pivoting the follower's right front corner in the right front corner of the magazine, slide the left front (rounded) corner of the follower under the left front magazine retaining tab;
7) With both front corners of the follower under the front magazine retaining tabs, tilt the follower and spring approximately 30 degrees to the right and hook the right edge of the follower under the right rear base plate retaining tab and tilt the follower and spring back to vertical. The follower should drop into place.
This procedure should require only light pressure. If significant resistance is encountered, stop, remove the follower and try again.