Ho Boy. Right now I'm thinking a picture says a thousand words. Let's see if I can do it in less than that......
You should have an L bracket with some holes in it, a smaller bracket with 4 holes in it (that's the left one) another bracket with 3 holes in it (that's the right one).
Looking at the back of your tractor where the fenders and seat deck mount to the rear housing you should see two brackets. Remove the brackets. Two bolts hold each bracket to the housing and one (15/16 or is it 7/8 I forget, should work) hold the seat deck
(should be a rubber washer/bushing isolating it). Find something to lift the back of the seat deck up (I use an overhead hoist, but I cheat) This should give you enough clearance to work.
On the left side of the rockshaft housing remove the two 17mm head bolts just forward of the 3 point top arms and install the 4 hole bracket through the existing holes. You'll need to use longer bolts due to the bracket thickness. Don't tighten them yet. On the right side remove the nut just fwd of the 3 point top arm and slip the right bracket over the stud and install the nut. Now remove the existing top link brackets.
Pay attention to the angle in the bottom of the brackets, that's how they go back on later.
Now take the large L shaped bracket (with the smaller holes on top and slide it over the top of the rockshaft housing, the 6 larger holes should line up with the holes of the top link brackets. Start the bolts in the upper brackets previously installed (may need spacers/washers between them). Re-install the top link brackets to the original position with longer bolts. Once all the bolts are started you can tighten everthing down and reassemble the seat deck.
Hope that made sense.......................