A 24x24 run will give you sufficient run space (570+ SF). Twenty 8' 4x4 posts spaced 5' apart, dug 2' into the ground and one sack of redi-mix concrete per hole. Where your door is, space those 4' and 4' in that corner, not 5" and 5'. Brace as indicated below (my run in progress last year)...
You will need bigger posts (4x4 minimum) and better wire (2x4 welded wire or no-climb fencing). Hope you saved the receipt. Chicken wire will keep the chickens in, but everything else will be coming in.
How many chicken do you have? Let's start there.