These are normally quite easy to replace.
Look at the handle on the side of the door and there you will see a small plastic cap.
Pop this off with a small screwdriver and behind there you will see a screw, Remove that screw.
Now pull the handle forwards and it will then unhinge from the other side as the other side is just a lug which slots in. Now sometimes removing it the lug breaks so dont worry about as you are replacing the handle anyway. Just make sure you remove the broken part from the door.
Then with the new handle just push the handle lug into the slot on the door and then push it back against the door and then refit the screw and thats it job done.
Hope this helps you.
If you look at the back of the handle you will see a cross shape. This lines up with the cross shape on the door.
Push the handle into the cross shape on the door and push it back and it should lock into the place and then you can fit the screw at the front from there.