The answer accept button is the star next to each answer (you can see this in the demo). And accepted answers are highlighted - in blue on this site but you can customise that to anything you like.
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask here, in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.