If you are looking to add a pop up store selector, or a pop up to choose between pickup and delivery use the following steps.
1. Log in as WordPress admin for the site you want to update
2. Navigate to Joint > Ecommerce
3. Update the Store selector behavior
3a. Manual - The store selector will pop up for users first time accessing the site, the location selected will be used as default moving forward.
3b. Sync - The store selector (if multiple locations exist) will geolocate the customer and assign the closest location.