I got a window unit for our bedroom and the instructions were of little use to me and frankly, they can not write instructions for your specific situation. I ended up cutting a piece of decking to fill in a space for the unit to rest on - otherwise it would be resting on a thin vinyl ridge of my window. Also made a support piece outside the window for the unit to rest on. I also installed a stop bracket for the unit to stop against to prevent it from falling out the window. I do not care for the idea of a heavy unit teetering on (and damaging) my expensive window ready to fall out should someone open the window. Also built some filler pieces because my window was too wide - they tell you the window can not be that wide (ha!). Get additional weather stripping as needed. Finally, I made a drip pan to make the condensate fall away from the house. As jeff mentioned, make sure the unit tilts back a bit or you will end up with a build up of condensate that your fan blade will spin through. So support, security, angle, and sealing it up. Probably your unit will be easier to install than mine - I think mine was worst case but still it did not take that long to put it in. Some photos are shown below.