How do I go from wifi to either an ethernet cable or thunderbolt cable?

terihartshorn wrote:

When I got to system preference I don't have an ethernet option and the thunderbolt bridge option says it's not connected. I have an ethernet cable going from my router to the thunderbolt adapter, then to my laptop. Am I doing something wrong?

Are you using an Apple branded adapter?

https://www.apple.com/shop/product/MC704LL/A/apple-usb-ethernet-adapter

For others who might find their way here by searching, that was likely an SMC reset:

How to reset the SMC of your Mac - Apple Support

.

In network preferences put Ethernet at the top of your list and of networks and your WiFi is second in the list then when you want to use Ethernet plug in the Ethernet cable. When you want to use Wifi, unplug the Ethernet cable.

If an Ethernet Interface is not shown, you may need to add the Ethernet interface to the left column of the display shown in:

System preferences > Network ..

... if not already showing, use the [+] under the box in the left column to add interfaces, and select your Ethernet Interface and add.

You must have your interface plugged in before the last Restart, or the Ethernet drivers will not load and Ethernet options will not be offered.

So stated the other way around:

plug in your adapter.

restart your computer.

try to add the interface again.