Please read the following article...
Cycle your salt tank
Once your tank is cycled, it is ready for A
fish. Add no more than 1 fish a month for the first few months and your tank will do just fine. Damsels are fine... if you want damsels!
Best thing to do before adding ANY fish... make up your "stock list" and research it. Is your tank the appropriate size for these fish? Which fish are more peaceful and which are more likely to be aggressive? Once you get your list finalized, THEN start to add fish - starting with the most peaceful and ending with the most aggressive. Adding fish in this order lets the less aggressive fish claim their territory and feel more at home before the big bullies get thrown in the tank. If you do it the other way around, the big bully will think the whole tank is his, and harass any new fish - possibly to the point of death.