Chlorine: either in the form of tablets(99%) or liquid (12.5%). OR Bromine but you still should use some liquid chlorine even with this. Muriatic Acid, CYA = cyanuric acid/conditioner Other items you may need or have to use depending upon how you maintain your pool: Soda ash, algaecide, tile cleaning soap, water clearifier. etc., etc.
usually just chlorine cyanuric acid to stabilize it, and some hydrochloric or muriatic acid or potash to balance it. the wisest thing to do is take a simple of the water to your pool shop and they will tel you exactly what you need .
you can add them in any order but DO NOT mix the chemicals they can cause fires the best bet is to test the water see what you need and add it to the pool one at a time then retest you may have to add chemicals several times in the first week or two until you get enough of a build up to sustain a clear safe pool. good luck
If you are unsure about the chemicals required in your above ground pool take a water sample to your local pool shop and they will set you on the right path
For starters? A couple of 1lb bags of "Shock-it" Chlorine tablets PH plus PH / Chlorine Test Kit ($10).
.chlorine