I don't have the Exede Voice adapter but on reading that, ensure that the yellow cable is used for the WAN connection between modem and voice adapter. Yellow Ethernet CAT5 cables are typically crossover cables rather than simple straight through connections (and since the directions go out of there way to mention specifically yellow I'll assume that's the case and pertinent).
Next comes the voice adapter to router connection. Using a regular straight through Ethernet CAT5 cable (typically blue, black), or gray) connect the LAN port of the voice adapter to the WAN port of the router.
After that you're likely looking at some additional router configuration but let's give the proper physical connections a shot first and you may get lucky out of the box.
If not comeback and verify the router brand and model and someone may be able to provide some additional guidance from the peplink manuals: