i have an ad i cant close

You can force close the app that the ad is included on. This explains how to force close an app.

Close an app on your iPhone or iPod touch - Apple Support

If that fails to close the ad, then I would force restart the phone. This will explain how to do that.

Force restart iPhone - Apple Support

Hello, Rcb9290, I am new in the Forums, but I have been using iPad for 6 years.

Do a hard reset. (hold down the power button and home button at the same time until the screen turns black with an apple logo in the center, this fixes most problems like this.)