Make sure that you previously uploaded the Sonaar theme before installing the child theme.
Step 1 – Unzip the file SONAAR-WP-PACKAGE.ZIP on your computer. You can download this file by login into your Sonaar Account > Licenses Keys
Step 2 – Once the file is unzipped, look into the /Theme/ folder and you will see the sonaar-child.zip which is the child theme that you will upload to your WordPress
Step 3 – Go to WP-Admin > Appearance > Themes and click on ‘add new’.
Step 4 – Select sonaar-child.zip file and upload it.
Step 5 – Activate it.