Mingle uses a system of layouts and if you are new to this kind of thing then it may confuse you at first until you get your head around it.
You need to make sure that the various areas WordPress sets up are set to use the appropriate layouts. Your different pages are displaying the same content most likely because they are all set to use the same layout. (Design Settings > Edit All Default Design Settings under the “Templates” heading.)
I recommend that you work through our “How to Make a Home Page with Mingle” tutorial because this provides a very good introduction to Mingle layouts and how the various components are brought together into a single layout. → http://para.llel.us/support/tutorials/how-to-make-a-home-page-with-mingle/
If you actually follow along with the article I think you will learn more than if you just read the article.
You won’t get the best out of the Mingle theme until you understand how layouts work so it is well worth putting in the time to learn, otherwise you may struggle. Once the penny drops, you’ll be off and away, I promise. Over the last five years I’ve given out the same advice more times than I can remember, but what I can remember is that as soon as you understand layouts and how the various components are brought together into a single layout, everything else just clicks into place. So please give it a go, in the long term I think it will save you time.