On your scream or message box, click the smiley face in the top right corner. This will pull up the emote list prompt. Click the blue carat to get the menu for the Icon Packs.
You will get a menu of the emotes on your phone. Click the emote package you wish to use.
This will populate the emotes so that you can click them and they will be put into your message/post.
If you do not own the emote pack, it will state it needs to be bought. You may purchase it at the addon gallery.