Set the two 37-inch boards on edge, parallel, 23 inches apart, and set the 23-inch boards on edge, perpendicularly between them so they're 34 inches apart. Screw through the 37-inch boards and into the ends of the 23-inch boards. Three screws should enter each end of the 23-inch boards. You should have a 26-by-37-inch frame with flush corners. This is the frame to your table top.
Position a timber perpendicularly inside each corner of the frame. These will be the legs to your hand jointer table. Screw four screws through each corner and into the timbers. The ends of the timbers should all be flush with one side of the frame.
Turn the table frame upright so it is standing on the timbers. Lay the plywood on top of the frame so the edges are flush. Screw the plywood to the frame using twelve screws total.
Position your hand jointer on top of the table so the blade jointer is perpendicular to the 37-inch sides of the table. Measure the distance from 26-inch sides to the jointer, as the must be equal. Mount the jointer to the table in this position. Use the mounting hardware it came with and the drill and drill bits if you need to pre-drill any holes for bolts.