If you want to create a Spirit House or learn about the tradition, see Steve Kinne's article.
Here's how one of us did this. We will call her Barbara, who didn't want to build a spirit house from scratch (some people will) so she looked around for an appropriate structure. Nothing there in her house but while walking in the pasture she found/remembered a birdhouse...perfect, that would do. Only not that specific bird house. It was occupied and she didn't want to evict the birds that were already living there so she took the idea and went to yard sales and feed and garden stores and looked on line until she found a bird house that fit for her Spirit House.