When your code stops at a breakpoint, you can step through it using the four buttons on the left of the toolbar:
In order, the buttons are:
- Play: run to the next breakpoint
- Step over: advance to the next line in the same function.
- Step into: advance to the next line in the function, unless on a function call, in which case enter the function being called
- Step out: run to the end of the current function