Faclan
If you soak in fresh water, there will be massive dieoffs..... very troublesome and stinks quite badly.
you can buy live rocks, sock it in Coral RX like what Peter mentioned.
If kiasu, after soaking, rinse it and you can leave it in open air (not under hot sun), occassionally sprinkling water to the rocks to keep them damp. Some of the surviving worms/ crabs should crawl out after a couple of hrs. Then take the rock, rinse with saltwater and put in your tank and cycle.
Dosing bacteria will help.