1. Connect PC to router and log into the router. Go to Network => Cellular.
2. Check “show advanced Options” and “Dual SIM enable”.
3. Scroll to the bottom, and create 2 profiles, ask the provider of your SIM cards about the APN, and fill in the blanks. If there's no special APN then it's just blank space.
Example: For example, if you have Verizon SIM at SIM1, and AT&T at SIM2, you are supposed to do this:
4. Scroll up and set up SIM1 Network Provider/ SIM2 Network Provider according to the SIMs you put in. (If both SIMs are same carrier/APN, just pick profile 1 for both)
5. Everything else could be left on default, then click apply at the bottom to save the change.