Configurations from the WAN side

[Ghstudio]

I run two networks locally...one VPN using opnsense (proxmox on a nuc) the other unencrypted through my internet providers gateway.  I have opnsense working with my VPN and I can reach the opnsense management page using 192.168.3.1 gateway/dhcp (I changed the opnsense gateway).  I would like to be able to reach opnsense management page from computers on my unencrypted network...which use the 192.168.1.1 gateway/dhcp on the main router.  I see the opnsense connection to the main router (192.168.1.xx).   How do I configure opnsense to allow me to connect from a computer on the 192.168.1 network to my opnsense (192.168.3.1) management page?