If you are currently a free user and would like to upgrade to Pro version from free theme then its quite easy. And the good news is All your content, theme settings will remain as it is even after switching to the Pro theme. You don’t need to redo what you have already built with the free version.

• Once you purchase the pro version you can access the theme download from your account page.
• Under Downloads tab you can see the theme download. Click and download the zip file of the theme.
• Go to Appearance->Themes
• Once you are on the themes page, click on the Add New button at the top.
• On the next screen, click on the Upload Theme button at the top.
• You will be prompted to choose the zip file that you downloaded earlier. Select the file and click Install Now.
• Once your theme is installed, you will see a success message along with the link to activate and preview the theme.
• Click on the activate button, and you’ve successfully installed and activated your WordPress Pro theme.