Summarize this article:

Plug one end of your iPad's charger cable into a USB port on your computer, then plug the other end of the cable into your iPad. Its app icon resembles a multicolored musical note on a white background.  If iTunes lets you know that there's an update available, first click Download iTunes and wait for the update to install. You may have to restart your computer before proceeding. If iTunes asks you to enter your passcode, you'll need to use recovery mode to wipe your iPad. You'll find this iPad-shaped icon in the upper-left side of the iTunes window. Doing so opens your iPad's page. If this is your first time connecting the iPad to iTunes, you may have to click Trust iPad and tap Trust This Computer on your computer and iPad respectively before continuing. It's in the "Backups" section. This will prompt your iPad to begin backing up to your computer; this process can take several minutes. If prompted, you might first have to click Transfer Purchases to copy any purchases music, shows, and/or apps onto your computer as well. This option is in the upper-right corner of the iPad's page. If prompted to turn off Find My iPhone, you'll need to use recovery mode to wipe your iPad instead. Doing so will cause your iPad to begin restoring itself to factory settings. If you're prompted to click Restore and Update instead, you'll have to click Next and then click Agree when prompted before you can continue. This process can take upwards of half an hour to complete, so be patient. Do not unplug your iPad or turn off your computer at any point during the restore. Once you arrive at the "Apps & Data" page on your iPad, you'll be able to select a backup option. To get to this page, you'll need to select a language, a region, and a Wi-Fi network. It's near the top of the "Apps & Data" page. If you have an iCloud backup available, you'll instead tap Restore from iCloud Backup. Type in your Apple ID email address and password, then tap Next to start the backup restore. Once the backup finishes restoring, you should be able to unlock your iPad by pressing the Home button, after which point you can set a new passcode. Once you've restored your iPad's backup and you're logged back into your iPad, you can disconnect it from your computer.

Summary:
Connect your iPad to your computer. Open iTunes. Click your iPad's icon. Click Back Up Now. Click Restore iPad…. Click Restore when prompted. Wait for your iPad to finish restoring. Follow the on-screen prompts to the "Apps & Data" page. Tap Restore from iTunes Backup. Enter your Apple ID credentials.