The routed package is actually just a frontend to the routed daemon for FreeBSD. To install routed in pfSense, navigate to System | Packages, scroll down to the table listing for routed, click on the Add icon for the package, and on the next page, click on the Confirm button. Routed should install in about two minutes or less.

To begin using routed, navigate to Services | RIP. There you will find a number of configuration options for the RIP daemon. Checking the Enable RIP checkbox enables the RIP daemon. The Interfaces listbox allows you to select the interfaces to which RIP will bind, so any interfaces that provide a path to another RIP-enabled router should be selected. The RIP Version drop-down box allows you to choose between RIP Version 1 and RIP Version 2; the RIP daemon will advertise and listen using whichever version is selected. The RIPv2 password edit box allows you to specify an RIP v2 password. The no_ag checkbox, if checked, turns off aggregation of subnets in RIP responses, while no_super_ag turns off aggregation of networks into super-networks. When you have finished making changes, click on the Save button at the bottom of the page.