New pfSense has three LAN rules, in this order:
Allow connections to the Web GUI on the LAN interface of the pfSense from any subnet
Allow traffic that is sourced from an IP address in the same subnet as the interface
(implied rule at the end of the list, does not normally explicitly appear) drop all traffic that didn't match one of the allow rules
You need to either change the default allow rule to allow every subnet you want, or add another rule that allows the subnet you're interested in.
Note that if your computers on the other subnet don't have some way to route traffic to the pfSense, you won't be moving traffic this way probably (like if those computers want internet access through this pfSense). You may want a virtual IP address on the LAN interface so that the pfsense has an IP address on both subnets to use, or something like that.