When I first started with VBox (to run XP) I went in blind and came out thinking "that was easy".
Once it's installed you do everything the way you normally do in XP. Setup firewalls, automatic updates, install software, etc. Before getting too far consider where you want to take snapshots of your install.
I took a snapshot after I installed from disk (but no updates) than again after I installed all updates and updates on the updates (which will put you at XP 3 and if you let it, IE8), and then one last snapshot, after I installed all the apps, tools, utilities, and any upgrades to those, that I use.