1. Figure out which QuickBooks you're on. QuickBooks Online (the subscription, browser-based version) and QuickBooks Desktop (the installed Windows or Mac software) behave completely differently on an iPad, so this decides everything else.
2. For QuickBooks Online, use the browser or the app. Open Safari and go to the regular QBO sign-in page, which works close to identically to a laptop browser, or download the free QuickBooks Online app from the App Store for a touch-optimized version of the same account.
3. Sign in with your existing Intuit account. Whichever route you pick, it's the same login and the same data; there's no separate iPad-only version of your books to set up.
4. Know that QuickBooks Desktop has no iPad version, period. It's not in the App Store under any name, and there's no mobile build of it the way there is for QBO. Desktop is built to run on Windows or Mac hardware specifically.
5. If you need Desktop on an iPad, use a hosting provider. A QuickBooks-authorized hosting service runs the real Desktop software on a remote Windows server, and your iPad just displays and controls it through a remote-access app, essentially a window into a PC running somewhere else. Desktop itself never touches the iPad; it's still running on Windows the whole time.
6. Or remote into your own PC instead of paying for hosting. If Desktop's already installed on an office computer, a remote-desktop app on the iPad (Microsoft Remote Desktop or similar) can control that machine directly, the same idea as hosting, just using a computer you already own instead of a rented one.