Enter and modify the program source code from within the built in editor. Then assemble the source code by selecting the Assemble command.
After successfully assembling the source code use the simulator to step through your program. You can watch registers, flags, ports and memory locations change as your program progresses.
You will see the flow of your program and be able to verify that it operates as intended. If it does not then return to the editor, reassemble and back to the simulator.