Using Puck as a single button keyboard

Have you read that quick start guide I've linked above? I think that would answer your questions.

Just want to clarify if following your instructions

You do need to upload as well.

• Copy code above to right hand side of IDE
  
• Connect to Puck
  
• Click the upload button
  
• Go to left-hand side
  
• Type save()
  
  

Then the code will run, but will also be saved.

If code saved then there's a way to clear the code or modify after save() action?

You can easily just connect and modify it right after, but in some cases (not the code above) you might be able to do something that stops you from logging in.

In that case, see this: http://www.espruino.com/Puck.js#i-saved-some-code-and-my-puck-js-no-longer-works