Forgot user id and password mynet N750

My technical knowledge is very limited  and my problem is I was able to set the router up 2 weeks ago  and I used the default password admin  password, but then it looked like I was connected unsecured, so I think I went into security in the setup and set up a username and password.  Now when I try to connect another laptop or my printer, it takes to the screen asking for user id and password and I can’t remember it.  I tried disconnecting the router uninstalling the software and re-installing and the using the default id and password, but still does not work.  Please help

do a hard reset - theres a hole under the router - bottom right corner - its very hard to see but its there

use something to do a hard reset - watch the power light - once it flickers the reset is complete so keep pushing till it flickers - when u do that, the default password wil be back to normal