which answer you are talking?The links you put in the answer will be "nofollow", so you can't use it for backlinks, but it can be a good way to drive traffic to your site. The answers are monitored, and spamming will get you banned. I believe you need to achieve a certain level before you are permitted to post a link. As you have no doubt notices, they are great rankings on google so it would probably be worth it to put in the time to create some high quality answers in order to be allowed to post a link at a later date.