Call a locksmith if you've no idea what you're doing.
If you know the drill point, or approximate drill point, go for it, but if you've no idea of the location of the levers within the lock case you may end up with a large hole!.
If the lock is a antique lever lock then it should not have a security curtain fitted to it,which means that the lock can be picked with either a set of wires or a two in one lever lock.Saying this though,if you have no idea how the lock mechanism actually works then you would not be able to pick it even if you did have the right tools.In which case you are probably better of drilling the lock.
Without knowing the exact make of the lock then i would drill a hole above the key hole roughly double the height of the key hole and slightly to the left.
