) Ensure that the mower deck drive belt tensioner lever is released. The lever is on the discharge chute side of the mower deck.
2) Attach the rear draft arms to the tractor.
3) Attach the front draft arms to the rod that goes through the holes in the front attachment mount points. Cotter pins mount through the rod inside the draft arms.
4) Attach the lift straps to the deck (assuming they're still attached to the tractor). The adjustable one goes on the left side if you need to reinstall them first.
4) (a) If you need to reinstall the lift straps hold the deck height adjust arm all the way forward/down. Install the lift straps through the hole on the lift strap and pull them down so they are engaged in the slot. Having a partner to hold the height adjust lever is a big help, otherwise tie it or use a bungee.
5) Reinstall the mower deck drive belt to the PTO. It takes some OOMPH to displace the deck drive pulley to generate enough slack to get the belt around the PTO.
6) Reengage the mower deck belt tensioner lever by pivoting it ~180 degrees to retension the sping that attaches to the two-stack pulley of the mower deck drive.