Okay, I understand the interfaces, however, Policies are designed at the beginning via zones. So, the itnerfaces you mention will be bound to zones..... you can check within the
network / interfaces / list and then look at the zone those interfaces are in. If they are both in the trust zone then you need a "trust-to-trust" policy. Within the policy, choose the network, protocols and anything else you want to allow through.
The default zones are:-
Trust
Untrust
DMZ
Your organisation may have created other zones and placed the interfaces within those. You will need th zone names before you can create the Policy.