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How to install the Child Theme?
A child theme is a theme that inherits the functionality and styling of another theme, called the parent theme. Child themes are the recommended way of modifying an existing theme. If you modify a theme directly and it is updated, then your modifications may be lost. By using a child theme you will ensure that your modifications are preserved.
How to install a Child Theme?
First of all, make sure that you have downloaded "All files & documentation" archive from ThemeForest:
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After you unzip the archive you will find a file "crexis-child.zip". That's the child theme.
Navigation to Appearance / Themes menu and click on the "Add New" button:
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On a new page, click on the "Upload Theme" button and the upload form will appear:
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Just select the crexis-child.zip file, click "Install Now" button and the upload process will begin. After it's done, just click on the "Activate Theme" button. Done!