No - never just pour salt into an aquarium. It would burn the fish and corals if you just pour it in undissolved. You don't have any inhabitants now but it's a good habit to get into of properly mixing, aerating, and aging your saltwater before adding it to the aquarium. As far as raising the salinity, you could top off with properly aged and prepared saltwater instead of your RO
water until you reach your desired SG
, or you could do a series of water changes with water prepared to 1.025 SG
. Whatever you do, make sure it's a gradual process. You're probably not going to see a change in salinity after just one water change, which is a good thing, especially if you did have animals in there.