Insert a post or something under the drill to support it while you assembly the rest of the drill.
Insert the bottom post/shaft into it’s place in the bottom of the main casting. Tighten it in place with the slotted set-screw.
Slide the drill table onto the shaft, tighten it in place with a square head set screw. Attach the bottom cast shaft support to the shaft also with a square head set screw.
Back together — at last!