(2-part post):
Place the barrel on the stillage, ensuring that it tilts slightly forward and that it can't rock about.
Whack a spile peg into the top of it. (I prefer soft spiles but, to be honest, I've never really noticed much difference if I've used hard spiles). In doing so, it helps to develop a technique so that the gas comes out of the barrel but the beer still stays in it! (Knocking a spile into a lively barrel, on a humid day in the middle of summer can easily result in an unexpected beer shampoo).
Some people like to tap the barrel at the same time. Others prefer to wait until the same day as the beer is to be drunk. If doing the latter, remember to remove the spile first, to vent the barrel. (Otherwise the pressure build up inside the barrel might result in the tap being pushed out. It's tricky enough to get it in, without losing any beer, anyway. There's no point in making the job harder!).
Leave for an appropriate time between putting the barrel on the stillage and drawing any beer off. Only experience will teach you how long 'an appropriate time' is. Most beers are fit to drink after two or three days. The longest I've known a beer take to settle and clear was 8 days. (If a beer is taking an exceptionally long time to clear,contact the brewery and seek their advice about the possibility of adding finings). Conversely, the record time for taking a barrel off the dray and drawing a perfect pint was under 2 hours!