You will need to remove the shell from from the rifle then you will need to remove the clip and then you will need to remove the bullet holder. After this all you have left is the shell and the handle. You can then clean as needed and reattach your gun.
underneath the trigger guard should be a flat head screw, when undone should release the trigger mechanism as well as allow access to another screw holding the barrel in place.
There are several ways to break this particular gun down. You will need to detach the amno and then remove the holder then you will need to remove the clip and the safety that is attached. Then the remaining parts will be the shell which is one big part all together.