What is most important when adding salt is to brush it around until it is dissolved? This is accelerated by turning your pump on, opening the bottom drain and adding the salt over the drain, rather than walking around the perimeter while adding the salt. It is recommended that you continue to run the pump for 24 hrs so the salt can spread evenly throughout the pool.
With Granular salt, 60-70% will have dissolved before hitting bottom. The remaining salt can simply be brushed into the drain which will then complete dissolution.

With all other forms of salt, it will take longer to dissolve but the same process will accelerate the dissolve rate. Simply brush the salt in a pyramid over the drain to increase dissolution.