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yeah, those are single addresses. You will need ranges, using CIDR notation, like 10.10.0.0/24, or simply a dash, like "1.1.1.1-2.2.2.2". Be careful with these, as it is easy to block too much if you don't know what you are doing, and really mess things up. As long as you don't block your access to the firewall, you can do a little trial and error if needed, though.
Facebook has so many IPs though, it's not even funny. They also use datacenters which other companies use, so in an attempt to block Facebook, you may be killing off hundreds of other websites and services running from the same datacenter, or another similar connection. Entire governments are struggling to block services like Facebook, so it's probably not going to be all that easy. This is still something good to learn, but would you be better off just using something like pfBlockerNG's DNSBL? With that, you can just specify that "Facebook.com" should be redirected to a dummy internal server, thus preventing access. For this to work, you do need to have your own DNS server, but pfSense makes that easy.
