The set of skins appeared unexpectedly with the release of Minecraft Pocket Edition 0.14.3 for Android, Windows 10 and iOS platforms. In the new version of the game, you will not notice any changes, except for a new pack — "Set of 2 settlers biome".
You can buy a set of skins for — $2. If you want to get a new set of skins, then you need to upgrade to MCPE 0.14.3. Also in this version, the developers have made several changes (bug fixes) — we don't know which ones yet!
I am a professional from Minecraft PE Team that creates and publishes the best content for Minecraft players. We have been studying custom gameplay, modding features, as well as popular game themes for a long time. You can be sure that our materials are designed for the player to spend more time in the game world than usual. Additionally, our modifications will allow you to turn your game into absolutely any other theme. I'm also a pretty good player, so I'll try to answer any of the questions in the comments.