If the rock is fully cured then you can just add it to the tank....If not you need to "cure" it. This involves letting it sit in a tank and cycle. Most people do 100% water changes to keep the ammonia and nitrites down to save most of the hitch hikers.
aaron
I would cure the rock first. Do you have another tank setup? Maybe a 10 gal? Put the rock in there for a month and then introduce it to your main tank. What is in your tank now? - fish?inverts?corals? - give more info - if only LR - then curing not necessary. Tank will mini cycle again though.