Click on Read More to find out how to link your image to a particular post (or other URL of your choice):
Go to your media library.
Click on the image you want to link.
In the bottom right, change the “link to” option to “Custom URL”.
Enter the URL you want and insert into post!
You need to remember that updating in your image library will NOT automatically update existing posts!
So, you will need to re-add images in your previous posts that you wish to link to URLs.