Restoring iPad will delete all the data from it and all the settings will be restored to factory defaults. So before trying to restore your iPad you should backup all your files from the iPad.
Make sure that your iTunes version is up-to-date and if it isn’t update. Connect the iPad to your computer and open iTunes. Select your iPad from the list on the left side of iTunes, it will be under section called devices. Then look for Summary tab and select Restore option. After that you can choose to backup your iPad but if you have backed it up already it isn’t necessary.