@apyleanne . This is easier if you use your ethernet computer.
In your browser, in the address field, enter:
This gets the router login screen.
The userid is admin in lower case.
The password is the Default Password shown on the label in fhe photo. It is case sensitive.
You will have to look for Band Steering. Disable it. Then change the 5GHz SSID by adding -5G
Then save. You should see 2 networks on your wifi device.