"If you registered before midnight December 20th, then click on the 24th on the Advent Calendar to instantly receive your gift - Lola Noel
The calender is on the front page, below Play button.
The Play button is on the left hand side on the small console with your clintz, credits, avatar, guild, BPs and so on.
The 24th is located on the top of the tree, in the form of a shooting star. It's very hard to miss.
The card will appear at 0xp, 1 star in your collection under the Berzerk
You get the the Berzerk
clan by clicking their clan symbol above the cards on the right-hand side. It's a red fist for those who don't know it.
If you want to level her up, put her to your deck. There's a link under her that says "Add to your deck." If it says "Remove from your deck" she's already in it. Then go to the Lost Warehouse.
The Warehouse is located on the newer game version, under multi player, on the third page.
Alternatively it's visible on the list of rooms if you're using the older version.