What to set "Source" to?

The source can be confusing until u get used to the idea.

Source Instagram will always display 20 (latest ) images from your instagram acc. You can chose to save these images in your media library by checking the tickbox under this option.

Source WP Media Library will use images from media library without checking instagram for new images.

I hope that helps.

So, if you choose WP Media Library, the plugin will cease to check your Instagram account completely? Or will it automatically add new Instagram pics to the library, and then use those?

I agree. The source option is confusing to me as well. What does “field above!” mean? The two options above it aren’t fields, they are radio buttons.

I logged in to ask a similar question about the media library option and found this recent post. Thanks to jetonr for answering but I already understood the “Insert Images” part. But the “field above!” text explanation isn’t clear.

I also noticed my site backups have ballooned recently and checking my media library I noticed lots of old Instagram pics. Do I have to delete those manually? Is that safe to do (i.e., it won’t affect your plugin)?

Suggested new wording for:

WP Media Library option will display previously saved instagram images for the user in the field above!

would be:

Choosing the WP Media Library option will cause the plugin to save Instagram images in the Media Library, and display those, reducing the loading time.

However, it’s still not clear from your answer above whether choosing that option will cause the plugin to cease looking at the Instagram account for more images. Logically, it should continue to look for new images and save them to the Media Library, but that is not clear.

The latest version has a better explanation on this issue!