Step 1: If you already have a clean, virgin installation of BlueJ 3.0.8, skip steps 2-3.

Step 2: Uninstall any and all existing versions of BlueJ by deleting the
folders "BlueJ 3.0.7" et al from /Applications .

Step 3: Download "BlueJ 3.0.8.zip" from http://bluej.org, unzip it,
and copy it into /Applications .  (NOTE: as of this writing, BlueJ 3.0.9
has just been released.  I haven't tried it yet, and I don't think it's
urgent to upgrade to it yet.)

Step 4: Run the installstuff.sh script in this folder.  It assumes that
BlueJ is installed in /Applications/BlueJ 3.0.8 .

Step 5: Run BlueJ and select "BlueJ"->"Preferences"->"Extensions".  You should see a section
about Checkstyle and a section about Submitter.  In the section for
Checkstyle, in the box labeled "Configuration File", there should be something like
"/Applications/BlueJ 3.0.8/BlueJ.app/Contents/Resources/Java/bloch_checks.xml"
or
"/Applications/BlueJ.app/Contents/Resources/Java/bloch_checks.xml"
If not, put in whichever makes sense (depending on where you put BlueJ.app).

Step 6 (optional, but would be nice): in the section for Submitter,
fill in whatever it takes for students to be able to send e-mail
from this computer.  For example, the server name should probably
be "smtp.gmail.com"; turn on "Use name and password" and "SSL".

Step 7 (testing): ... maybe you'd better have somebody from the CS department test the installation before you roll it out.