before fragging get gloves and safety glasses. yes, it is that serious. zooanthids and palythoas release a palytoxin which is harmful and it has potential to "shoot" or "squirt" getting in your eyes.
with that aside clear a table or space and lay down a towel, get paper towels, alittle bowl with tank water, fragging glue (or gel super glue) and a razor blade works well. your going to want frag plugs, disks, rubble rock or peices of tile to mount the frags. a dremel is a great tool to frag too! simply just cut off a piece of the main colony and you have a frag.
remove the colony your fragging, put into bowl with tank water. dry off the plug,rubble rock or whatever your attaching it to if wet. now take the colony and try to carefully get under the polyps one by one and carefully glue them on a plug without getting glue on their openings. the polyps will be fine outside of the tank for 10 or so minutes so dont worry so much about that and if need be, dunk them in the bucket of tank water. frag and return to tank and leave them to heal for awhile.
again, wear gloves and goggles and take your time! goodluck