Engine sleeve, I guess you mean liner? If so, Take out the liner, replace ring on piston, replace piston and then instert liner over piston and slide down.
When you remove the liner you'll notice that it has a tapered bottom edge that slides easliy over the ring.

If you can't remove the liner but have managed to replace the ring, you can get some strong fishing line or pull-pull cable, slide piston down until the ring rests on the liner and then make a loop out of the trace passing it around the ring.
As you pull on each side, you'll compress the ring and you'll be able to push in the piston using your thumbs.
Fiddly, but it'll get you there.