First make sure you have a surge protector and make sure your plugs are not close to your tank. Remove everything from the box, put small parts in the bag with the warranty info and manual. Place your tank where you want it to be- make sure if you are placing it on a table or something that it can support the weight of the aquarium when full. Assemble your filter (usually pretty self explanatory), place the light in its spot on the clear plastic/ glass part of the hood- you may have to pop the hinged opening on, or you may find that you have an all in one hood, in which you just put it on top of the aquarium. Line up where there is indication for the filter and the heater. Remove the hood, rinse gravel, sand, marbles, etc for your substrate. Fill your tank about a quarter of the way up and either a) use a cup, fill it with your substrate with as much water removed as possible and holding it straight up and down until it fills in with water at the bottom of the tank and gently pour or b) use a pvc
pipe and syphon it in (2 methods I have had personal success with). Place any plants or decor now (remember the suggested depth of substrate is 2 inches). Begin syphoning in water- I have a preference to do this slowly using the filter so as to not disturb what I just put in. Plug in filter, heater and light. Voila.
Things to remember-
Always use a water conditioner that removes chloros and heavy metals, preferably something that has slime coat protection. Seachem Prime, Nutrafin Aqua+, Kordon NovaQuel, API Stress coat+ are my personal faves
Fish in or Fishless cycle. Do your research and find out which one you think would be the best for you.
I would suggest at least one air stone or decoration for air dispersal.
A master test kit for your type of tank (fresh, salt or reef) is a STRONGLY RECOMMENDED item for your sanity, consensus here says API master test kits are the preferred kind.
RESEARCH YOUR LIVESTOCK. Know what you are getting into. Look at pictures online (liveaquaria.com can give you some good ideas and give you some statistics on the types of fish you're interested in along with compatibility) and ask around at your lfs
Enjoy your hobby, and have fun learning. Hope I helped a little!!