when I started playing guitar learning chords was the first thing I did
it takes time. how much time depends partly on how much you practice but even the most committed guitarist will take some considerable time to master open chords
the good news is that all that practice is toughening your fingers, strenghening your muscles, improving flexibility and getting your fingers used to the size shape and feel of the neck and the frets
the thing to remember about chord changes is that you have to practice until your fingers move between chords almost without you being conscious of that - and for that to happen it has to be a comfortable and economic movement
for example A to E. whenever you make that change you will turn your wrist, your first finger will drop a fraction and your second and third finger will rise simulataneously. Ideally there should be no other movement in the hand or fingers - its an almost graceful transition.
its worth watching guitarists make chord changes
look the beginners videos at
http://www.justinguitar.com/