@vitor-geronutti
There seems little need to write such thing in a manual.?
1 - Create a backend
2 - Add 2 servers to the backend
3 - Create Frontend, and select the default-backend made at step 1
4 - configure a ip:port for the frontend to listen on
5 - configure a firewall rule on your WAN to allow access
Done?
If not please share your haproxy.cfg, and check on the stats page that servers are up.
Troubleshooting: https://github.com/PiBa-NL/pfsense-haproxy-package-doc/wiki/haproxy_troubleshooting