When I started playing guitar about two and a half years ago I learnt a lot very quicky, this website had a lot to do with this. However it took me a good hard two months practise to master barre chords.
These are hard chords to master and I'm sure any guitarist will tell you the same. One of the main problems for a beginner is getting over the pain barrier in your fretting arm. Unfortunatley the only thing I can say is bear with it, because your arm will get stronger and eventually the pain will cease.
I have set up this short lesson to try and explain the way I learnt to deal with barre chords when I was starting out. I'm not a brilliant teacher, this is my first lesson and you could probably find better ones on this site, but hopefully this will help you.
Above you will see an F Major chord
This is a useful chord to know because you can find it in lots of songs. It is also a good barre chord to learn from.
The first thing to is to put your hand in place and strum. Don't be surprised if you hear an awful sound. This is quite natural, your hand is probably not applying enough pressure to the strings. By doing this you can begin to find how your hand should be to achieve the proper sound. You will probably find this painful and awkward to do. As I said before, the pain will go in time, so chin up! As for awkwardness, maybe you need to adjust the postion of your wrist to allow to play the chord. It is important that you learn to get a decent sound so that when you play it in a song you won't spoil the tune with an unwanted rasping sound.
The next step is to learn how to switch to barre chords from other chords. There are two ways to do this:
1) You can start by placing your barre finger (the finger you are lying on the strings) on the neck in the position required and then the other fingers afterwards.
2) You can start by placing your non-barre fingers in place and then the barre finger.
Personally I would recommend the second option. The reason I say this is because accuracy is harder to achieve with your non-barre fingers rather than the barre finger. The barre finger has a larger area for position, therefore there is more room for error.
Of course the other option is to lay all fingers in position at once but this is very difficult and will probably come with time if you learn the way I have suggested.
I hope this has been of some use to you. You may not take my advice but perhaps it will help you find a way that you are comfortable with.