If you do not have a data plan for your iPad, then there are three ways to download to the iPad...
1. You need to connect it to a WiFi network. If you do not have a wireless internet modem at home or if you do have one but did not set it up, then you need to do so.
2. Use a public WiFi network; not very fast and not as secure as your own private WiFi network. For example, Starbucks has wireless service for customers. Simply walk into one of their stores and use your iPad to detect WiFi networks. I believe public libraries generally also have wireless service for free, but it has been a long time since I've been to a library.
3. Download whatever you want to down to a PC/Mac, then use iTunes to transfer to the iPad.