How can I install/configure my dotProject to be able to access it via the server URL You should not make any alterations of your config files. dotProject should be able to work via the IP of the server where your account resides. If you have installed dotProject in your public_html folder you will be able to access your installation via the following link:
http://serverip/~username/
where serverip stands for the IP of the server where your account resides and username stands for your username.