You did say you want to install a patio cover but you didn't say to what extreme you want to go. If you're talking about instructions on how to install a permanent overhang where you need to do rafter work, sheathing, shingling, support posts, and the like, I don't know of any place where you can find or borrow 'instructions'. Every home is different and would best be done by a pro.
Another option is to get a retractable awning. They can be installed as a do-it-yourself (dyi) project. Camping magazines and I know the magazine put out by The Family Handyman have advertisements in them for this type of awning. They come in a variety of sizes and styes. An advantage to having one is if you want the sun to shine on the deck, it can retract. Before you rule this option out, you ought to at least look at one. Some are manually retracted and others are push-button. There are a number of neat features that have been employed for home use. It kinda rolls up out of the way. If you've ever been to a campground and seen travel trailers with these awnings extended along side the trailer, this is the same principle.
Now, I know my initial comments are a bit 'disappointing'. BUT, all is not lost. If you choose to go the route of wanting a permanent patio cover, see if the contractor can do just the rough work. If you and your 'help' is handy, you can do the roof sheathing, papering, and shingling yourself. There is PLENTY of info on the WEB on how to do this. Plus, you can paint it too. Get 2 or 3 contractors to give you a COMPLETE estimate, then get them to give you a watered-down one. Don't tell them you want the 2nd one until you get the 1st one. Some contractors will give you prices that are pretty close to each type of estimate to discourage you from doing work that 'makes money'. I would suggest that you have the contractor do the necessary work for tying in the new roof to the house AND whatever work is necessary to make sure there won't be any water leaks. If you want to do this part of the job, you need to find out what you should do. If you mess this part up, you'll have a river at the seam where the patio cover meets the house. PLUS, you run the risk of doing damage to the main house too.
In any event, if there's anything else I can do, post up. My best to ya and hope this helps.