@killast 

If you bound the TP-Link ID to your router you would use the password for your TP-Link ID.

What you can do is remove the Tether app, do a factory reset on the router by holding the reset for 10 seconds. When the router comes back up, use a computer, either wire to it witha Ethernet cable or connect to the wireless network, the wireless password is below the router (8 digits). 

Here is a FAQ to log into the router: https://www.tp-link.com/en/support/faq/1523/

Other then using http://tplinkwifi.net you can also use http://192.168.0.1 or http://192.168.1.1

Any of the above should get you the login page where you can log in and then set it up.