if you just load an .hdl file, you are in interactive mode: so you need to set the input values yourself, and press Single Step (single arrow) to see the result. If you want the perform all the available tests in one go, you need to run the test script: so to test Not.hdl load Not.tst and press Run (double arrow).
Whenever I put the logic after editing the .hdl file and try to load it into the simulator, it stops responding. It says, loading chip at the bottom of the screen and nothing happens. It is not able to load the .hdl file