The MedPlus Lite is a free WordPress theme build in WordPress customizer whereas the MedPlus PRO theme is built in more user friendly Theme Options panel. The PRO version contains lots of sections in home page for creating beautiful and professional website.
With PRO theme you can use all your previously created posts and pages. After activating the PRO theme you will need to configure your site with the post and pages using Theme Options panel.
After activating the MedPlus theme, setup homepage using following
Go to Settings -> Reading -> Front page displays
Click on radio button of Your latest posts
Go to Appearance -> Theme Options and click on Restore Defaults in bottom side
Please check the documentation to customize the PRO theme