Switch to the Staking-only guide. You do not need to install or run BOINC in order to use GRC as a cryptocurrency.
In order to earn more Gridcoin, you need to crunch one or more whitelisted BOINC projects within team Gridcoin. You must install the BOINC client!
Navigate to the BOINC website, download and install the appropriate BOINC client on each of the computers you wish to crunch BOINC work upon. If you're not crunching projects which require VirtualBox you don't need to install BOINC+VirtualBox.