Aside from some new buildings and decorations, CityVille is celebrating the holidays by giving every player a free Christmas tree for a new game goal. The first part of the new Holiday Tree goal is called "Place the Holiday Tree" and it's really simple. Just go to the user panel on the bottom right, access the inventory, click on the Holiday Tree and drag it into your city to install it. This will pay you 50 Coins.
Part two is called "Growing the Tree" and to complete it, you'll either need 20 City Cash or have 10 friends willing to send you a "Present" each from the "Free Gifts" page.
You can notify your friends that you need presents by clicking on the "Growing the Tree" goal icon on the left hand side, then "Ask Your Friends" to post to your wall. But be careful -- if you cancel the wall post instead of allowing it to post, you'll lose the "Ask Your Friends" option, because that button will turn into the message "Waiting for your friends to respond", which means you won't be able to click it anymore. Friends who answer your wall post for gifts will get 50 Coins for helping you. As for you, the more presents you get, the bigger your tree will grow!