Assuming you have the connection between the FusionHub and the BR1 in place.
Log in to the admin page of the FusionHub, and go to the SpeedFusion status page. For the link you will see it listing the LAN address space of the BR1 (the other end of the connection) as published by the BR1 (192.168.2.0/24 in this example):
Assume that the webcam has IP address 192.168.2.110 (provided by the BR1, and not changing). Then all you have to do is forward the appropriate ports from the WAN IP address of the FusionHub to the appropriate port (which may be the same) of the camera. E.g.:
In this example some ports are mapped straight through to the same port of the webcam, other ports (such as 8090) is mapped to a different port of the webcam.
And the latter is one way of handling multiple webcams (or services generally): You decide how to associate ports with specific webcams, and then perform a mapping for each from the WAN IP and the port you chose to port 80 (for http) of the LAN IP of the associated webcam. (An example from a different router, were 192.168.11.0/24 is the LAN address space of the router with the six webcams having IP addresses 192.168.11.21-26 ):