While looking through the function reference entry for wp_insert_post(), I noticed that there's no parameter in the array it requires which will allow me to set the 'Featured Image' for a post, displayed as the post thumbnail in my theme.
I have looked into functions like set_post_thumbnail(), as suggested by Mr. Bennett, but this seems to be a relatively new addition to WordPress itself and the WordPress codex. As such, there aren't any sources that I can find which explain how the $thumbnail_id parameter should be acquired and supplied. If this really is the function to use, in what way could I provide it with a valid $thumbnail_id parameter when all I have is an image URL?
Thanks in advance!