The stickers and 'smileys' have been combined into one icon.  Click on the 'smiley' icon at the lower left to launch the new emote panel.  To use your emojis, click the emojis tab.  To use your stickers, click on the stickers tab.

Smileys or 'emoji' packs as well as sticker packs are listed at the bottom of each panel.  Scroll up or down to select the pack you want to use.  You can also search by name if you have lots of stickers.  Use the shopping cart to go to the virtual gift store to get more!