Time to open up some code and do some editing. This assumes you have some code already written, and ready to be edited. If not, hop on over to Github and clone something. Go to File->Open Directory and select your project's directory. You can open files individually, but the directory tree display is very handy.
To jump between files, you can point and click on the left, select open files via tabs on the right, or use Find File. The shortcut for the Find File feature is Ctrl-T on Linux and PC, and Command-T on OS X. This open a dialog where you can type part of the filename and select it from a list. This is often the most efficient way to switch between files in larger projects.
It's often useful to edit one file while looking at another file. In Redcar, the feature that allows you to do this is called a Notebook. To open a new notebook, go to View->Notebooks->New Notebook. The editor window will be split in half vertically. You can then drag tabs to the new notebook. If you prefer the notebooks to split the editor horizontally, you can go to View->Notebooks->Rotate Notebooks.
There are a number of interesting editing options in the Edit menu. Be sure to explore Edit->Line Tools, Edit->Formatting and Edit->Formatting->Convert Text.