From here you can select from over 1200 software packages to install. The buttons in the bottom-left corner of the window allow you to:

Expand the tree view

Collapse the tree view

Toggle between a flat view that lists all packages alphabetically, or sorted into groups.
You can navigate the list and choose software packages entirely using the keyboard.
Use the "page up" and "page down" keys to scroll through the list one screen at a time, and use the cursor keys to highlight a package which displays details of that application.