Hello!
putting on a ring is easy!
Just take apart the engine so you have the piston in your hand. Check the pistonring slot in the piston so no dirt is visible .....Then!
Take the new pistonring
and lay it on top of the the piston. Then press the ring apart somewhat so you could push the ring over the the piston on just one side.....just a little.......Do this carefully! Then carefully widen the ring somewhat more and push it over the piston so that it seats in the slot in the piston.
That's it!
This is more easily done in practice than it is to write about........

Regards!
Jan K
Sweden