Enter IP address of your raspberry and click "Connect"
Now you can choose "Raspbian" OS and install it. Icon of card inform you that image of this OS is on microSD and there will be no nessesary to download files from internet. Other OS will be downloaded from internet during installation. Raspbian takes about 3,5GB (remember, that NOOBS files will still be in microSD).
Option 2 - automatic installation
Put silentinstall on the end of first line in recovery.cmdline file
After you insert microSD to raspberry (connected to power) Raspbian installation will begin. This process can take 30-60 minutes.