I'm guessing you are still in the early setup stages of your tank? If so, then you can get away with dumping the salt right in your tank. 2 things to take note of though... 1) make sure you add it slowly so you don't get too much salt in the mix; and 2) make sure your water level is lower than you would normally like to keep it. The salt will displace water and cause your level to rise. Also, having it low will give your room to add more water if you should get too much salt added.
In the future, you should mix up the saltwater in a separate container, then add it to your tank.