Thats easier described than done. Tons of patience, good husbandry and tons of calcium. That is coraline algae. You can get scrapings from local fish stores, or fellow hobbyist. The later is normally the way to go. It is highly beneficial as it dosent allow other less desirable (pest) types of algae to grow. There is a wealth of info on the web so just search for it. Then reply back here if there are any questions left. Also it doesn't hurt to check the helpful articles section. Link at top of this page. Hope this helps.

well number one that picture was taken by revhtree, So alot of photoshoping helps, but seriously the best thing is patience. usually if you keep your alkalinity and calcium up coraline will start to grow after several months, buying some premium live rock covered in coraline will help boost the growth. but the tank needs to be well established before even worrying about coraline, its basically a sign of a well established reef. and can take years to get a beautiful coating of coraline. my problem is as soon as my rockwork gets covered in it I change something and have to move all the rock around and start all over. anyway hope this helps