There is some element of "plug and play" however, that setup is likely to be very insecure and some devices may not connect if they have been configured for some specific requirement such as a static IP.
Do you have the 2660's User Manual?
I found the following link via D-Link:
https://www.dlink.com.br/wp-content/uploads/2019/06/EXO_Manual_v1.00WW.pdf
Verify that that is the applicable User Manual for your router.
Then you will need to read through the manual and plan out, as best you can, how to connect and configure the router for your wired and wireless needs.
What make and model modem do you have? That must also be taken into consideration - some modems are also routers ( i.e., a "combo") and having two routers can create problems.
Sketch out the connections you have made and note the corresponding configuration settings as well.
Normally the connections will be something like the following line diagram:
ISP --- Coax/DSL cable ---> Modem --- Ethernet cable--->[WAN] Router[LAN] --- Ethernet cables---> Wired devices and ~~~ wireless~~~> wireless devices.
Here is a "how to" link that may prove helpful:
https://www.lifewire.com/how-to-set-up-your-home-wi-fi-network-2378223
You can easily find other similar links. Do so as necessary to keep track of both the "big picture" and the details therein.
Again, plan it all out first and then work through it all step-by-step. Keep notes and address any specific problem or question as you go. Focus on getting internet connectivity restored. Doing so will be easier via wired connections.
Once you know that internet is available/working then any wireless issues with respect to internet connections are likely due to your wireless configuration.
Step by step. Post as necessary if you encounter some problem that arises.