The iPad's software does not allow use of most computer mice. The Apple staff designed the iPad as a touch-based mobile device, and that touch interaction is a large part of what separates it from other computing devices. This software does not support mouse use, in part because cursor and mouse interaction require different programming from multitouch.
Connections vs. Support
Because iPad offers Bluetooth connections for peripherals such as keyboards and headphones, you might expect that these connections could work with a mouse too. However, the software that supports mouse-style pointer interaction with the screen is not present in Apple's iPad software. Apple's USB camera connection kit also offers users a way to add a limited USB port to the iPad, but again, even if you can connect a USB mouse to the device, the software drivers are not available to support it.
Mouse-Like Tapping Precision
Inserting the cursor at a certain point in text can be difficult for some users, especially when the software snaps your cursor to the beginning or end of the word you tap. For precise cursor insertion, nearly all iPad apps support magnification mode. Simply hold your finger on the area where you want to insert the cursor rather than tapping and releasing. A magnification window will appear, allowing you to slide your finger to insert the cursor exactly where you want it. Releasing your finger snaps the iPad back to regular view so you can continue typing.
Other Mouse Features
You may miss the ability to right-click or secondary-click on the iPad, but again, there are touch gestures that mimic this property of a mouse. For example, if you hold your finger on a link in an iPad browser or document, a right-click-style context menu appears, allowing you options such as copying the link or opening in a new tab or page.
Considerations
If you find finger-tapping and gestures uncomfortable, try one of the many styluses available for the iPad. These allow a more pen-and-paper type of experience, rather than finger taps and can reduce hand fatigue from the unaccustomed gestures. You may hear of users working with mice on "jailbroken" iPads. Jailbreaking is against Apple's terms of service and will void any warranties and support for your iPad, as well as reducing or eliminating certain Apple services.