Never email or text your user credentials for any device or site. Neither is secure. Do not let a browser store (remember) them either.
So ... How do I close that Rogue Antivirus pop-up?
Sometimes referred to as "scareware", this program often appears in a fake window reporting to you that you already have hundreds (or thousands) of viruses on your PC. The unsuspecting user is then encouraged to purchase an antivirus product designed specifically to address the problems.
At this point, we have at least two facts: anything you click on this rogue window will be a mistake, and the attempted purchase of such is actually the worst decision that could be made because then the perpetrator will have all of your credit card data on the card you use for this transaction.
While it may be likely that you have some portion of this virus infecting your PC, you can avoid making it worse. Click nothing on this fake window. Instead, close all your open programs and then simultaneously press the [Alt] key and the [F4] key. This Windows-based keystroke combination is a command to close the active window.
Whether or not the rogue window closes, reboot your PC. You might get lucky and your existing (legitimate) antivirus software identify and remove this threat. If not, there is work to do. Be deliberate with your actions. Seek a knowledgeable professional for assistance as needed.