You can donate/enter by going here. You'll need to donate a minimum of $10 to Julia's House in order to be entered into the drawing for a chance to attend the AGE OF ULTRON premiere. There are some pretty cool perks for those able to donate higher amounts, so if you're looking for some nice AVENGERS: AGE OF ULTRON exclusives, you can always donate more. (And by more, I mean a lot more than the $10 minimum.)
Donate some cash for a good cause and you'll be entered for the chance of a lifetime.