There are three "skins" or templates currently installed.hmmm. I didn't see a button like that - but - I clicked that 'AW Drift' and chose 'Xenforo'; when I resized the text flowed all the way to the right side.
AW Drift Dark
You can chose them from the bottom of the forum page (the specific location depends on the template) or from your Profile. Click on your your avatar on the top right, then Preferences then Style.