On your 'App settings' tab you have a drop-down box for "Default blog to display". Pick the one you want and that ought to take care of business.

Thank you for your quick reply.

I would like the blog to show up as follows www.mysite.com instead of www.mysite.com/blog/index.php

Is there a way to do this?

Yup. Move everything from inside the "blog" folder up one level, then change your $baseurl in your conf/_basic_config.php file.

Thank you!