After installing VirtualBox, and if you do not already have a BOINC client installed click in the below links according to your platform to set up correctly your BOINC client. Otherwise, you will have to install the BOINC client first. In this case go to the BOINC download link on the official BOINC site - this should detect your running operating system, automatically choose the best client for your computer, and give you a link to download an installer package. Note that the setup process differs from one operating system to another, so before double-clicking in the installer, please use the following information depending on your OS:
After all the above installation steps, the BOINC client can be launched and you will be ready to attach your BOINC enabled computer to the project.