Take the feet off, should be either an allen key or a cross head screwdriver.
Try to remove all cushions if possible, usually you will find they are zipped on at the back but if they are stitched don't worry too much. Normally these big yokes are assembled in sections, so if worst comes to worst, remove the basecloth (which will be really cheap to replace if you Fcuk it up, in fact you won't know it isn't there when the sofa is in anyway) and have a look inside. If you are really lucky it will be in two pieces bolted together. Remove bolts, lift pieces, reattach bolts.
I have delivered sofas most of my life, never beaten yet