That motor is pinned on the intake side of the motor, and towards the back, between the rear main intake port and the boost port, make sure the piston is pointing that way where the pin is, they came with an arrow on top of the piston pointing the way, but you can just scribe another one in if you cannot read it
The rings are cut on the back side at the gap to clear the pin so the gap goes at the pin. Some engines like the ST 51 have the rings cut about an 1/8 in away from the gap to clear the pin, so double check your motor BEFORE you install the parts .,
IF you buy a ring from a aftermarket ring maker, and he machines the pin clearance in the WRONG place, and tells you to twist the sleeve to match, just look for a new ring that is stock
Be aware some engines the ring has top be install top to bottom correctly, there is a top and bottom to some rings
Many of ringed pinned engines have a bevel cut on the bottom of the sleeve to compress the ring as you slide the sleeve over the top of the piston and into the case, this is doen ALWAYS at top dead center, and you make have to twist and wiggle the sleeve a very SMALL amount to get the ring to compress. CAUTION many people ding or break the ring installing them as they are too aggressive with the technique to install them
Check the ring by just squaring them up in the sleeve and using a feeler gauge,,, DO NOT use a dental pick
Regards
Randy