New to debugging

I am new to the debug 'step into' looks useful but how can 'edit' the lines numbers it complains about, since I have to come out and then i just have the code minus the numbers....

questions:

1 can you 'turn on' the line numbers in the edit mode?

2. If not how do you edit from the 'step into' mode

3. What's the right hand smaller window showing certain lines etc doing

In Plato:

Tools > Settings > Text Editor > General > Show line numbers (Check box on)

Tools > Settings > Miscellanous > Integrate with SGDB (Check box on)

By clicking on the elements of the right hand box you can see the values currently assigned to variables.

You need to exit the debugger to allow editing of the source code.