Instagram Stories is a feature that allows people to post photos and videos for 24 hours. Then, they disappear completely from your feed. If you don't want them to disappear after the deadline, then you can save the stories as a "Highlight".

Prior to the update, you had to share your Instagram covers in your stories to set them as covers for your highlights. You can now select a cover from your phone camera roll. No longer do you need to spam people with these covers ... yay! Unlike regular Instagram stories, highlights are saved to custom categories on your profile. Let's begin.

I have added a new stories category (Cheese Garden). Instagram automatically chose a cover photo from a screen cap of one of the stories. 

1) Hold your finger on the highlight stories.

2) Select “Edit Highlight”

3) Select “Edit Cover”

4) Click on the “image” icon on the left

If you have a lot of photos and videos in the highlight. Scroll to the left for the image icon. 

5) Select the highlight icon (you want) from your photo gallery

6) Select the photo, and then click on "done".

Volia! Custom highlight cover is up, and you did't annoy any of your followers =)