You now need to add an alias to apache's httpd.conf pointing to
%%SQUIRRELDIR%% in order to access SquirrelMail from
your web browser, or create a VirtualHost with DocumentRoot set to
that directory.

For SquirrelMail to work properly you will need to make sure the
following option is set in your php.ini file:
file_uploads = On

If you have problems with SquirrelMail saying "you must login" after
you just have, the following php.ini option may help:
session.auto_start = 1

In order to do your administrative configuration you need to 
cd %%SQUIRRELDIR%% && ./configure
SquirrelMail will not work until this has been done. After this
step is complete, and the config.php is created, plugin ports will
properly auto activate.