When setting up Closeby in your Shopify store, we automatically will use your currently active theme. This is a limitation with Shopify, so we are unable to install Closeby onto your other themes when they aren't the actively published.
However, once you have published a new theme for your store, you can easily reinstall Closeby to it right from your Closeby account.
First, go to your Closeby account's installation page: https://www.closeby.co/maps/install
Then, scroll down to one of the Shopify instructional sections such as "Theme Section"
Next, open it and click the link to reinstall Closeby.
Confirm your active theme and submit the form.
That's it. You should see it updated in your new Shopify theme.