You recently posted these pictures in another thread. You can clearly see that the first picture is a filthy freshwater setup, there are goldfish swimming in the tank. It's possible that the second picture is phytoplankton, but there's really no way to tell from that picture.
You can not simply just add salt and make it a saltwater tank. The tank needs to be properly cleaned and re setup with the proper equipment. The gravel that's in there now, for example, will not work for saltwater. I suggest that you read through the Recommended Threads in the New Hobbyist section to start learning what is involved with setting up and maintaining a saltwater tank.