Custom layout for postpage

I would like to use a custom template for the post-page. My website has one column, the page where al the posts apear has got to have two columns. So far i’ve made the file, linked it to the post-page but nothing happens.

If I link the template to a ‘normal’ page it al works just fine. I do know how to use a custom template for single posts page but I have no idea how to get it to work with the page where al posts are displayed.

Hope one of you guys can help me out.