Lower Alkalinity in pool

I NEED TO LOWER ALKALINITY IN ABOVE GROUND POOL…DO I HAVE TO USE MURATIC ACID AND IF I DO POOL PUMP OFF OR ON? ALSO POOL IS DIRTY A BIT DO I NEED TO CLEAN WITH POOL VACUUM FIRST BEFORE ADDIND MURATIC ACID?

Hello Pool2018 - We would recommend cleaning/vacuuming the pool as much as possible before adding any chemicals. The pump should be running when the muriatic acid is added to the pool.