From here you can select from over 1500 individual 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.

View the description of a package in the right panel by clicking on a package name with the mouse. Select a package for installation (or removal) by selecting the checkmark after its name.

Press the floppy drive icon to load selections that were saved during a previous installation.