How do I install a tv on my wall

First of all find out what size mount is on the TV. On the back of the TV you should see 4 screw holes to take the bolts of the stand. You can measure the space between the holes. Then you can search for a mount that will take that size. If the TV is big you will need a very strong wall mount.
When you get the mount it should have instructions for mounting it. But make certain the wall you are fixing it to can take the weight and is stable. Fix the mount to the wall, make certain that you use the correct screws and plugs for the screws. You should be able to tell if the mount is secure enough. If you have any doubts, get somebody in to do it. The mount will come with the correct fixing screws for the TV. You will need two people at least to fix a smaller TV to the wall and two people to hold a big TV while a third screws the mount to the TV.