You can easily create breakpoints in the source editor by double-clicking in the gray column on the left hand side of the editor window. A blue dot will appear in that column, next to the source line. In this context, you may find it useful to add line-numbers to the source view by selecting Window -> Preferences, expanding the node General -> Editors -> Text Editors and selecting "Show line numbers."
Note that you can create breakpoints before beginning your debug session.
The other primary way to set breakpoints is with the Breakpoint view. In the following, that view is shown below the Debug view.
You can also set breakpoints by right-clicking on the space to the left of the source line and using the resulting contextual menu.
