Magazine Theme moving and how to change / add more buttons


So i fixed the issue with my theme i had before started over now when im on home page the blog is centered but when i click on members etc the blog moves to the right and becomes off center how to i fix this, example below.

Centered :

To the right :

Also how to i change the button “magazine” in the menu up the top to something else and can i also add more buttons to that menu?

Thanks guys