If your sprockets are OK, then keep it simple:
Get the bike upright, with the rear wheel off the deck.
Loosen the adjusters and move the rear wheel forward towards the frame again, slackening the chain.
Split the old chain near the back and connect the new chain to it.
Slowly pull the old chain out, allowing it to drag the new one into place.
Close up the new chain, adjust for free play as normal, lube up and go for a ride!!