Proxy mapping configuration file may be editted directly using any text editor. But it may be more covenient to use Foxy web-based Proxy Mapping Editor.
Point your browser to http://foxy/proxies (actual host name may be different, depending on the value of the pseudo_domain parameter defined in the main configuration file.)
Click Add Maping to add a new mapping.
Click on the name of the mapping you want to edit. Functionality of the buttons on the bottom of the form should be self-explanatory.
Click Clone to make a copy of the current mapping.
Click Raw to switch to raw editting mode. In raw mode proxy mapping configuration looks exactly like it looks in the proxy mapping configuration file.
Click Form to switch back to form mode. In form mode you don't have to know the exact parameter names, you just enter values. List parameters (e.g. include) are editted in text boxes, one value per line.
Don't forget to click Apply before moving to another proxy mapping.