Cannot use my keyboard. Must have disconnected something. Only lets me type on screen. How can I type on my keyboard

You did not tell us which iPad, and Keyboard that you are using. It is very hard to formulate an answer based on your short post.

If your keyboard connects to your iPad over bluetooth then disconnect/remove/forget the keyboard from the bluetooth list and then reconnect it back to the iPad. See whether that helps.

Axel F.