How to supply obj.setOwner()

I have trouble finding how or what I should supply obj.setOwner().

From some digging I found that obj.getOwner() returns a "PropertiedUser". Is that what I should supply the setOwner?
If so how do I make PropertiedUser out of a string?

I saw that page, but it doesn't say how to get the user object or member object from a string.
For example if I have the username is there method to return the PropertiedUser representation of that username?

Edit: Found it: