Here you can find the instructions on how to switch your store to another one.
➤ To set Magento 2 theme as default, follow these steps:
1. In your Magento store Admin Panel go to the Content > Design > Configuration.
2. To set the default theme in a Website level, press Global Main Website > edit in the Action column.
3. Select “Your Theme”(example) from the Applied Theme option dropdown, press the Save Config button in the top right.
4. Refresh the Magento cache.