This is a link to the Girard instructions:
My added suggestions:
The Girard instructions say to remove the end caps but do not tell you how. The slide cover awning end caps are plastic and have 4 small protrusions that press into the metal ends caps (first pic). Mine also had white silicone sealer on them from the factory. Gently pry the plastic end caps off with a small screw driver.
You will need to purchase a tensioner tool from Girard. It looks like a 3/8" square drive tool with a slot cut into it for the center spring screw.
First release the tension on the spring so you can properly re-tension it.
To re-tension the spring. Girard says to use seven full turns. In reality, you will put fourteen 1/2 turns counter clock wise on the spring. Again, use the 3/8" wrench to hold the tensioner tool while you reset the ratchet.
After this you can test the new cover by retracting and extending the slide.
If all is well, you can glue the plastic end caps back on. I used 2 small pieces of Gorilla tape to hold the covers overnight.
Link to thread on replacing the slide out cover fabric. It has pictures that may be useful.
Hope this helps!