Instagram doesn't have any "Unfollow All" feature or option in the app, so there isn't a way to unfollow everyone at once. As a result you can't mass unfollow users. So if you want to know How To Unfollow Everyone On Instagram, then you have to manually unfollow up to 200 accounts per day by clicking on the "Following" button, next to their names in your following list.
Here's how -
1. Tap on your profile in the Instagram app.
2. Click on the "Following" Section and it represents the list of people you're following on Instagram.
3. Tap on the "Following" button, next to the person's name and tap "Unfollow" when prompted.
4. Repeat the process for each account you want to unfollow.