Usually, Facebook pick featured image as a thumbnail image from the article which you shared or someone shared. But, sometimes it may take a random image from your article that is not comfortable all the time.
By using Yoast Seo Plugin, you can fix the problem in a proper way. To implement this, you have to go and click SEO option in the left sidebar.
Then you will find a page which is covering social media issues. From there, you have click on the Facebook option. Then it will take you to Yoast SEO meta box on the post edit screen.
Here you can choose a Facebook thumbnail image for your homepage. You can make your own choice by using this option.
This is how you can choose a thumbnail image and add accordingly.