I'm not even sure if you can. Unfortunately, Weebly is one of the many web builders that doesn't care much or at all about accessibility. There are several other serious problems for screen readers on your website, that I don't think Weebly will allow you to fix. So long as you stay with them your website can never be truly accessible. If possible, you should seriously consider moving to Wordpress. Wordpress websites are accessible by default, and they spend a lot of time making sure they stay that way.