Login into Learnyst as Admin and from admin dashboard go to Website builder ---> More ---> Settings ---> A Title & URL ---> Favicon.
Click on Upload New Image. You can upload image from your local drive. Click on Select. The favicon image is updated in the Favicon image field.
Once done click on Update button. Success message appears and then Click on Done button. Then Click on Go Back button and you can Save and publish the changes to your website.