Change Router Username and Password

Product Information
NETGEAR WN1000RP

I realize this is an older extender but it has been working just fine! I watched the news and they said to change the password on your Internet router because we are being hacked! So, I changed the password on my AT&T Internet router and then the extender didn't work on my iPad which is about 400 feet from my main computer. (That's why I purchased the extender). I don't know how to change the password on the iPad, so I opened the NETGEAR Genie application on my big computer and was not able to find where I update my AT&T Internet Router information. I found a username and password on the Genie app on my iMac as "admin" and "password". That's terrible! I want to change that as well. HOWEVER I need to know how to update the AT&T Intgernet Router password so my Netgear Extender works on my iPad. Can someone help me without telling me I have to pay more jusgt for that information? I was on tech support for 45 minutes during a work day and no answser!