The -t4 can be changed to whatever value works best for your machine, you'll have to have a play to work it out !
instead of: type cd /var/lib/boinc-client
do this: type cd /var/lib/boinc-client/projects/www.cosmologyathome.org
That takes you straight to the project's folder.
Then type: sudo gedit app_config.xml
and fill in the stuff you want, should be able to see how to save and exit the editor !
typing: cd ..
will take you up a folder level.