Open the list you want to download.
Navigate to the tab you want to download: Instagrammers, YouTubers, TikTokers, or Twitchers.
Find the green Download button, in the top right corner.
Click it, and you can choose if you want to download your list as a CSV or XLS file.
The metrics Heepsy provides are slightly different for each network. This is why you have to download Instagram profiles separately from YouTube, and so on.