Fill the hydrometer with tank water and bang it on a flat surface, then leave it a second and see were it settles, give it a few flicks too if you aren't sure the reading is correct.
Then simply throw it in the garbage and get a $20 refractometer on eBay and be glad you listened to the good people on this forum. Joking aside, I am a saltwater noob and a refractometer is just way better and easier to use, I am glad I went ahead and got one.
As for testing I use the API test kits, I use the freshwater master test kit because all but one of my tanks are fresh but the saltwater master test kit is the same thing. They are easy to use, you can test pH, Ammonia, Nitrite and Nitrate with them. It will set you back $20-30 but has about 800 tests between the whole kit. Just make sure you grab the Saltwater master test kit not the Reef master test kit (unless you are going to be adding coral down the line then get both)