Hi there and welcome
to remove the adds you need to pay as you see, and to do this please do the following On your computer
Sign into your account at www.amazon.com
Under "Your Account" click on "Manage Your Kindle". Then on the left-hand side of the screen, under "Your Kindle Account" click on "Manage Your Devices". This will bring to a list of all the kindles linked to your account. There is a column on the list titled "Special Offers". You just need to find the appropriate row for your Kindle and then click the setting under the Special Offers column. Follow the prompts to pay your $ that it indicates and ads on the lock screen will be removed.
Pop up adds though are not from Amazon. These will be from an app installed, usually a free one, so locate an app you installed around the time you started receiving the popups, uninstall the app and this will remove the popups.
If you have any problems, or would like any additional information or assistance, please do not hesitate to let me know.
Else if you can take a second to rate my service by clicking one of the stars at the top of the screen then submit, that would be greatly appreciated.