|I di not generally deal with all-in-one's but I would assume that there is an access hatch to the memory somewhere on the back similar to a laptop that may have one or two screws holding it closed. If it is there, then the manufacture intended this to be a consumer upgradable portion so that your warranty will not be effected.|
You can go to Asus' website and see if there are images or videos of this for you.
You can go to Crucial.com and scan your system to find out what memory you can use for your system.
Try here http://www.service.asus.com/#!downl... to find your exact model number and see if your manual is available and is should be of help for you on this.
You have to be a little bit crazy to keep you from going insane.