Do you put an apostroph s after 2 words to show ownership of the next word?

Yes, when two Words jointly own a subsequent noun, you typically add an apostrophe and "s" to the last Word. For example, in "John and Mary's house," the house belongs to both John and Mary. If ownership is shared by both, you only add the apostrophe to the second noun. If they own separate items, you would add 's to both, like "John's and Mary's houses."