if the tv had a remote and it been eaten by the couch,go to walmart or any store that sells universal remotes and google the remote code for your tv. you should be able with the right codes to control the tv so you can change inputs while sitting down.
You seems to have 2 questions: How to hook up, and how to control.
Hook up: Just plug it in, I don't understand the problem. Pick a HDMI port on the TV.
Control: Already discussed by members. Hopefully the manual buttons on the TV does it otherwise you will have to get a remote substitute or hell buy one from Sony? If this is an out of production TV I believe there is a place on the Net which sells old, original remote, GOOGLE is your best friend.