Hello mivec, the first thing to find out is to check whether the caliper is still working or seized up, jack up the car and spin the wheel and then get somebody to press the brakes, if every thing is OK the have a look at the caliper and ascertain how many pistons it has, if it has one piston have a look at the face that presses onto the pad. If the piston has 2 cutouts then the piston has to be pushed and screwed back with a special tool. If you can't get a tool you can turn the piston with a pair of water pump pliers or vise grips, and press it at the same time, be careful not to damage the caliper rubber. You will find it slow going but better than nothing. I hope this helps.
regards johnwr