I don't think Oproject uses a vbox wrapper for their tasks. If you want to run their tasks, you will have to install vbox, as F$ explained. Then you will need to build a client. A virtual computer. I recommend Mint version of linux. Then once you have that up an running inside vbox, you rub BOINC on that VM, just like you run it on your real computer.

Edit, as for detailed instructions, there is too much to go into here. I suggest irc or that team chat thing, and ask someone to walk you through it real time.