It has been a while since I did this, but I wanted to add another calendar to my ipad. Right now I have 2 that I use and it works great. I can show both or hide one or the other. I recently received a calling in my church that prompted me to create a separate calendar to mor easily track related activities.
Adding the additional calendar turned out to be easy, but It did take a minute to research. You simply visit http://m.google.com/synch from your Ipad and you will see a list of your calendars and your shared calendars. You can check the ones you want and when you visit the Calendar App on your ipad those that you checked will show up.