After you’ve downloaded the theme Avaris, Navigate to your WordPress Dashboard and head to Appearence >> Themes, Then click on Add New
Click on upload theme
Click on Choose file and navigate your PC to the directory containing your Avaris Download, then hit Install Now.
WordPress should start uploading your theme, wait for it to finish and go to then next step.
Navigate to your Themes under Appearence again, you’ll find your new Avaris theme installed, hover over the theme’s thumbnail and click Activate.
if you’re having trouble uploading the theme through WP due to memory limitations on PHP or WP itself, please check out ftp installation guide.