AAAAAaaaahhhhhh.....now I know what you're facing.
Looking in your user manual, in Chapter 2, page 8, Section 2.2, you will need to complete steps 1 thru 5 just as described, however, on page 9, Step 6, - SKIP METHOD 1: Wired -
and take a good look at Method 2: Wirelessly
.....there are two steps:
- first look on the bottom of the new TP-Link 1750 router and see what the name (SSID) is that your new router will be transmitting, and take note of the default password that is also written there....
- now go to your computer, pull down the WiFi fan to find that SSID (TP-Link_XXXX -or- TP-Link_XXXX_5G), click on it to join and use the password that you just took note of from the label on the bottom of the router.
Once you complete those two steps you are ready to move directly to Chapter 3.
In Chapter 3 there are two steps listed on page 12.....the first step is done on your computer in the Networking PrefPane of System Preferences, however, you are most likely ALREADY configured just as they describe - to get an IP address automatically - so really you can probably just skip this step and everything should work just fine.
The second step is where you got confused in your first (and subsequent) attempt(s) to get the new router online....the URL you are pointing your browser at <http://tplinkwifi.net
> is NOT found on the internet, it is found inside the firmware of your new router and is a web-based configuration tool that your new router is broadcasting just for you.....it is only accessible from your Local Area Network, not from the internet side.
The first thing it will present you with after you click on "Let's get started" will be a place to set a password for logging back into the control tool later....don't worry about any of the other stuff about having a TP-Link account, as you don't have one and won't need one unless you want to start adding on those other features later.
Once your password is set, you are in Chapter 4 and you should now see an option to setup your internet connection - choose the Setup Wizard and it will lead you through the rest of your setup process.
When you are done with the wizard, you should be able to reach out on the internet to let us all know how it all went. If that doesn't seem to work, then have your stepson do his phone service with you on Monday to answer any questions for you.
....and for your safety net, simply keep the old Belkin WiFi router close at hand to plug back into your system and regain your old setup that was working before. This should not be needed, but it is an easy fix if things don't go the way you want with the new router.
So what do you think? Hit it, or wait for Monday?
Let us know.