your 180 is a nice size to start with as a beginner, but dont get in over your head. this tank is going to cost you a lot of money but dont be discouraged.
1. pick out the place you want the tank to be and put it there on the stand.
2. get about 100 lbs of live rock. you should be able to make small mounds throughout the tank but dont put them any higher than a little under three quarters of the height of the tank. this is because fish swim in open waters and need that above space to act as their open water, rock is just for hiding.
3. get about 100lbs of live sand.
4. put both the live rock and live sand in the tank and fill with saltwater.
5. let the tank sit for about a month with the filter running and power heads running before you add any livestock, test throughout the whole month.
what you will need for a tank this size is 2-4 goos sized power heads to make sure there is good water flow and no dead spots in your tank. a regular filter wont do for a tank this size, you are going to need to buy a sump and make an over flow or buy a reef ready tank which is easier. a heater is necessary to keep the right temperature. if you have any other questions please let me know.