You must try to hold the strings down only enough to make them sound cleanly and no more.
By doing this the hardest part of your finger will be in contact with the string and you will not need to use so much force.
Purchase a grip master or buy a squeeze ball and use it for a few minutes each day. This will improve your finger strength dramatically.
Another tip is to buy a decent guitar. If you're trying to learn on a bad guitar you will probably find guitar barre chords very hard or even impossible When your guitar action is very high holding down the strings to play a barre chord will be very hard. On the other hand if the action is too low, you will struggle with the 'buzzes' and 'clicks'.
Another tip is to use lighter gauge guitar strings.Heavier guitar strings will make holding the barre tougher.
If you're just starting out it is a good idea to learn barre chords on lighter gauge strings first. If your guitar is rubbish this step is essential.
Most people begin by learning the dreaded F barre chord But you can be smarter then that. Try practicing barre chords by learning further up the neck and slowly moving downwards to the F chord position