I have answered on one question in Magento Stack Exchange. The user got the solution from my answer.
Everything is fine till now. But, The user got one error message as minimum limit 15 reputation.
How he can upvote and accept?
User can not do upvote in any post till they got 15 reputation on that
stack exchange site.
and Also upvote is based on situation if you like someones answer then you can upvote.
Its not always necessary to upvote and accept answer some one answer.
and also you cannot force someone to accept and upvote, you can just request someone if they like your answer then accept