Download the jQuery Modal Image plugin from GitHub repository and unzip the folder. You get there in the folder two files, one
modal.js, and another is
Open the file with your favorite code editor and change the class with your image class name. For mine, the image class name is .img-frm img. Copy this CSS code and paste at the below in your theme’s style.css file. Save the changes.
Do the same job for the modal.js file, change the class with your class name. After changes upload the file to your active WordPress theme directory. If you found any js folder put the file into it.
.Now, let’s call the jQuery file. Open theme’s functions.php file and add the piece of code below.