Full page

Hello everyone. I am trying to realize my website, finding in the Clean Magazine theme the right one. I was been able to make all the various setting of the parameters in a way useful for me, but I wasn't successful in obtaining a text that occupies the full page. It seem like my site was been on 3 columns with only the right showing the text, as you can see in the screenshot below. Anyone could help me please? Thanks a lot in advance.