Practicing these chords
Getting these chords memorized is just the first step. In order for them to be useful, you'll have to learn to move from chord to chord fairly quickly. This will take much practice and patience, but you'll get the hang of it!
Once you've reviewed these chords thoroughly, move on to learning a new strum. The main reason most beginners have trouble switching chords quickly is because of wasted movement in their fretting hand. Study your fingers when moving from chord to chord. Chances are, one (or a few) of your fingers will come way off the fretboard, and often hover in mid-air while you try to decide where each finger should go. This is unnecessary, and can really slow you down. Now, try again... play a chord, and BEFORE you switch to another chord, visualize playing this second chord shape. Picture in your mind exactly which fingers will need to go where, and only after you've done this should you switch chords. Pay attention to any small, unnecessary movements your fingers make, and eliminate them. Although this is easier said than done, your hard work and attention to detail will start paying off quickly.