- If you have a customized theme, say "MyTheme", then modify theme.xml to make MagentoClara inherite from "MyTheme" by replacing
<parent>Magento/luma</parent>
with
<parent>Magento/MyTheme</parent>
- Put the MagentoClara files under
__/magento2/app/design/frontend/Exocortex/MagentoClara
- Add and apply MagentoClara theme from the admin portal, under Content->Design