Pagina dinámica para ingreso y borrado de información

Hi. I need a huge help. I do not know much about programming, but I’ve gotten myself into a maze with this and I must solve it soon.

I have created a page in which only the members of the site can have access. Each one must enter certain data and must have access to delete them also from a database, but all this in a single dynamic page. It works well for a single member, because it is a single database, but I do not know how to do so that each member can see or delete only their data and not the others. In fact I do not know how to do it so that they can erase their data from a dynamic page.

Can help me?