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you're on the wrong forum. try re-posting this to revit architecture forum.
Walls, ceilings, and floors are system families. You don't create them from a family template. You select a wall type already in the project (or project template), select Edit Type from the properties palette, select Duplicate, give it a new name, then edit the structure of the wall to be what you want.
Before you do that, I'd recommend spending a few days reading through here on some of the basics of how modeling in Revit works. There's a lot of good content there.