How Do I Put An App I Wrote On My iPad?
You would have to pay around 100$ (annual) for iOS Developer Program in order to upload Your app to the device. You won't have to upload it via AppStore but directly from Xcode. 

You need to pay, because Apple provides You all neccessary Provisioning Profiles, Certificates etc. You'll be able to add up to 100 iDevices to Your account.

Here's knowledge base with all informations.