How to get a Mini Monument Campfire:
1.Open your steam library and right-click dont starve (singleplayer)
2.click "View CD key"
3.Click "Don't Starve Reign of Giants" and copy the key to clipboard
4.Open Don't Starve Togheter
5.On the bottom right corner there is a button saying "redeem"
6.Click it and write the previosly copied key.
7.Now you should get a new campfire skin.
The skin looks like this: