They can be obtained by completing missions, watching ads (although it almost never works), sending votes and confirming photos (sometimes that doesn't work either)
You can confirm photos here:
There are a total of 50 photos to be confirmed, and they will ask questions about each one.
If they manage to reach 50 (because sometimes they leave on their own before then), they will be given 100 votes.
Don't forget to upload photos too, so the other Stays can confirm them, and no, as far as I know they don't give votes for uploading photos, or at least they haven't given them to me.