Ok, all the parts are to be glued and then nailed together. You are nailing into the edges of plywood, so, use 6d finish nails and be carefull that they go in straight.
First make the tray.
Glue and nail the bottom of the tray between the two tray sides.
Next, glue and nail the sides to one of the ends, then add the tray to that end as well.
Flip the end over so the sides and try are pointing up into the air, and glue and nail on the other end.
Glue and nail the bottom to the ends and sides. Then slip in the dowel and glue it in, and add a nail down into it from the edge of the end.
Let me know how it turns out!