Interface assignment for VOIP traffic shaping over the site-to-site OpenVPN

[morgenstern]

I am trying to set up the traffic shaping for the VOIP on a site to site OpenVPN link from a branch office to our HQ.

Netgate SG-3100 appliance is the branch office VPN client device.

Following the official guide I got to the point where I assigned an interface to the OpenVPN and after confirming it, lost the VPN connection.

https://docs.netgate.com/pfsense/en/latest/book/trafficshaper/traffic-shaping-and-vpns.html
https://docs.netgate.com/pfsense/en/latest/book/openvpn/assigning-openvpn-interfaces.html#firewall-openvpn-int-assign-config

I just want to clarify the necessary steps to restore the VPN connectivity after the article says:

Navigate to the Interface configuration page, Interfaces > OPTx
Check Enable
Enter an appropriate Description which will become the interface name (e.g. VPNServer)
Select none for both IPv4 Configuration Type and for IPv6 Configuration Type
Note: This will not configure any IP address information on the interface, which is necessary since OpenVPN itself must configure these settings.
Click Save
Click Apply Changes
This does not change the functionality of OpenVPN, it makes the interface available for firewall rule, NAT, and gateway purposes, among other uses.
After assigning the OpenVPN interface, edit the OpenVPN server or client and click Save once there as well to reinitialize the VPN. This is necessary for the VPN to recover from the assignment process.

Do I simply go to the client OpenVPN setup and switch the interface from WAN to the one that I have just assigned?

Will it then pick up the site to site OpenVPN ruleset I have in place? Also, will I need to create any separate FW rules for the newly assigned interface? The guide is a bit unclear on this.