These two buttons provide you with URLs that look something like this: https://builder.eachscape.com/data/collections/nn.xml where the part containining nn is replaced with unique integer.
If you choose Yes for the Public Feed (on the Edit Collection Page), you will find that the provided URL works without logging into the EachScape Builder. However, if you choose No for the Public Feed setting, you will not be able to use the URL as it is. It is necessary for these so-called private feeds to have an API key. You can obtain an API key on the Api Keys (the rightmost button on the screen shot. The API Key you obtain can be added to the URL as the parameter apikey= added to the URL supplied. When you use the apikey= parameter, it is required that you also include the https protocol at the beginning of the feed URL.
Another, simpler option is to use an automatically generated Remote data source. For these data sources the URL of the data source will be updated to contain the appropriate URL to include an API Key when you indicate the collection's feed is not public.