Are you trying to stream to the ATV or from the ATv to an Ipad?
If to ATV you need a computer running Itunes and setup for Home Sharing, If to an IPAD from ATV, I do not belive that is possible, you can AIrplay from Ipad to ATV but I don't think it works the other way.
The ATV can stream from Videos that are stored in icloud and associated with the Apple ID logged into the account.