Upgrading altars?

So i got impatient waiting for the ps4 release so got it on xbox one to make the time go quicker. So i have a altar of ymir and have just learned the next one. How do i upgrade . something happened to my original now its gone. But i cant seem to build the level 2 one. Do i need the original to build over

Yes I do believe so.
The upgrade installs from inside the Alters inventory.
Original Is in your inventory with other building options.

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If you build the next tier altar inside the existing altar, it automatically upgrades.