Having never used BOINC aside from very briefly, what do I need to do?
Do you have a recent version of BOINC installed ?
Can get latest for your machine/OS from here:
http://boinc.berkeley.edu/download_all.php
You don't need the Virtualbox option for Enigma, can always add it later if you want to do CERN type stuff later.
Once installed, run it and set it to Advanced View, add the Enigma project from the list, follow the prompts to create your account, set your team (that will be OcUK !).
If on Windows...
Stop the project from downloading more work (set No new tasks), you should only get 1 task to begin with anyway. Abort it unless you want to wait for it to finish. Once aborted/finished, exit BOINC. See Hanluc's post on page 1 to get the optimised app and copy all the unzipped files into the hidden folder C:\ProgramData\BOINC\projects\
www.enigmaathome.net
Restart BOINC, set project to Allow new tasks, wait a few minutes whilst Enigma sorts itself out !
Fine tune preferences on the client (ie 24 hours full steam ahead !).
Check work is completed and reported and you appear in the team on the Enigma website.
Hide or don't hide your machine(s).
If not hidden you can be helped to spot problems and see if running the optimised app, your choice.