Pick one of the available programs to load, and click 'Load'.
Upload your own .cas file, by clicking 'Pick a .cas file'.
This makes the program available for cassette input.
Issue NAS-SYS command 'R' to load the program into memory.
Click 'Rewind', to allow for multiple 'R' commands.
Execute the program with the NAS-SYS command 'E1000' (typically)