At this point, you can select any subset of software you want to install, or just scroll down to the bottom and pick "Everything" for a full install. Note that, based on what you select, there is a size display at the bottom of the screen that shows you how much space this install will take.
It's not critical to install all of the desired software right now - you can always install additional software as you need it after the system is up and running.
It's also definitely worth knowing that the vast majority of the installation will be under the /usr directory, so if you configured the disk layout to have several filesystems, make sure you allocated enough space in the /usr filesystem.
Once you make the software selection and click to continue, you are officially passing the point of no return, as the next step in the installation process is to re-partition the drive(s) and format the new partitions with new, empty filesystems. At any point until now, you could have abandoned the install process with no changes to the disk layout by just rebooting with the key sequence Ctl-Alt-Del.
In addition, once you see that the new filesystems are being created, you can switch to virtual console five which, at this point, displays a running commentary on the creation and formatting of the new partitions.