all you need is to have the apache module, dav_svn enabled. ln -s into the sites-enabled folder under /etc/apache2.
This gives you http access to svn.
Setup with SSL ideally.
also in /etc/apache2 is the dav_svn.passwd file.
give this as the necessary argument to htpasswd to add users to access subversion. This will not grant them ssh access to your system.
These are not all the steps you need to take to protect your system, but these are at least all the subversion related ones...