To glue up, find the corresponding aprons and legs, start by putting a small amount of glue onto the tenons, spread this with a thin scrap of wood, then put some glue in the mortise hole. Use the chisel hammer to help you seat the joint then apply a clamp once you have both the legs in place.
Once you have glued up 2 of the aprons, you can move on to gluing the other two. Be mindful that the clamp can close up the mortise hole slightly so remove the clamp before you glue up this part.
Tip: You can use a block to rest on the shoulder on the tenon to hammer when seating the joint so you don’t have to hammer the mitred tenon.
When the last part of the frame comes together, use the soft face of the hammer to seat the joints.
Put a clamp on each side, make sure the clamps opposite each other line up.
Check for square by measuring corner to corner (adjust the clamps until it is the same measurement both ways) then leave to dry overnight.