If your purchased theme is using genesis framework (has genesis.zip in the folder you downloaded), upload Genesis Framework first (step 1) then upload the child theme (step 2).
If your purchased theme doesn’t need Genesis Framework (doesn’t have genesis.zip in the folder you downloaded), continue to step 2.
PS : If you’re on WordPress.com Business plan, follow this step here (wordpress.com is a bit different than self hosted wordpress).
1. Installing Genesis Framework
Download the .zip file. Do not upload this file yet or you will receive this error message “The package could not be installed. The theme is missing the style.css stylesheet.” It means you upload the wrong zip file.
Unzip/extract the file you downloaded using Winrar or Winzip.
After you unzip/extract the file, you will see these files, extract these to your local computer (example : your Desktop).
Go to your WordPress admin page, Appearance – Themes.
Click Add New
Click Upload New (Upload file : genesis.zip)
After you successfully installed the theme, don’t activate Genesis yet. Return to the Themes Page and proceed to Step 2.
2. Installing SkyandStars Theme
Go back to Appearance – Themes. This time, upload the Child theme (themename.zip) and activate it.
At this point, you already has your new theme installed. You will see that your layout looks messy. It is normal and it happens because of the widget arrangement from your previous theme. You can re-arrange/edit your widget after this.