To get to the debugger, load a sample app from the SDK, and then telnet into your Roku on port 8085, then hit ctrl-break. On a Roku2 device, you may need to load the sample app twice, as ctrl-break sometimes exits the debugger the first time.
If you want a completely-from-scratch setup to work from, duplicate one of the example folders like simpleinfo, rename it, change the name of the project in the Makefile to the same name as your renamed folder (make sure not to leave a space on the end of the name) and replace the contents of the .brs file with:
sub main()
stop
end sub
Then when you load that channel you should go straight to the debugger and be able to experiment.
- Joel