Copying the HTML and add into editor and update content following Use HTML Into Editor
<!-- Start Gallery Area -->
<section class="gallery-area pt-100 pb-70">
<div class="container">
<div class="row">
<div class="col-lg-4 col-md-6 col-sm-6">
<div class="single-gallery-item">
<a href="https://edmo.envytheme.com/pluginfile.php/2/course/section/1/img1.jpg" class="popup-btn">
<img src="https://edmo.envytheme.com/pluginfile.php/2/course/section/1/img1.jpg" alt="image">
</a>
</div>
</div>
<div class="col-lg-4 col-md-6 col-sm-6">
<div class="single-gallery-item">
<a href="https://edmo.envytheme.com/pluginfile.php/2/course/section/1/img2.jpg" class="popup-btn">
<img src="https://edmo.envytheme.com/pluginfile.php/2/course/section/1/img2.jpg" alt="image">
</a>
</div>
</div>
<div class="col-lg-4 col-md-6 col-sm-6">
<div class="single-gallery-item">
<a href="https://edmo.envytheme.com/pluginfile.php/2/course/section/1/img3.jpg" class="popup-btn">
<img src="https://edmo.envytheme.com/pluginfile.php/2/course/section/1/img3.jpg" alt="image">
</a>
</div>
</div>
<div class="col-lg-4 col-md-6 col-sm-6">
<div class="single-gallery-item">
<a href="https://edmo.envytheme.com/pluginfile.php/2/course/section/1/img4.jpg" class="popup-btn">
<img src="https://edmo.envytheme.com/pluginfile.php/2/course/section/1/img4.jpg" alt="image">
</a>
</div>
</div>
<div class="col-lg-4 col-md-6 col-sm-6">
<div class="single-gallery-item">
<a href="https://edmo.envytheme.com/pluginfile.php/2/course/section/1/img5.jpg" class="popup-btn">
<img src="https://edmo.envytheme.com/pluginfile.php/2/course/section/1/img5.jpg" alt="image">
</a>
</div>
</div>
<div class="col-lg-4 col-md-6 col-sm-6">
<div class="single-gallery-item">
<a href="https://edmo.envytheme.com/draftfile.php/5/user/draft/942015966/img6.jpg" class="popup-btn">
<img src="https://edmo.envytheme.com/draftfile.php/5/user/draft/942015966/img6.jpg" alt="image">
</a>
</div>
</div>
<div class="col-lg-4 col-md-6 col-sm-6">
<div class="single-gallery-item">
<a href="https://edmo.envytheme.com/draftfile.php/5/user/draft/942015966/img7.jpg" class="popup-btn">
<img src="https://edmo.envytheme.com/draftfile.php/5/user/draft/942015966/img7.jpg" alt="image">
</a>
</div>
</div>
<div class="col-lg-4 col-md-6 col-sm-6">
<div class="single-gallery-item">
<a href="https://edmo.envytheme.com/draftfile.php/5/user/draft/942015966/img8.jpg" class="popup-btn">
<img src="https://edmo.envytheme.com/draftfile.php/5/user/draft/942015966/img8.jpg" alt="image">
</a>
</div>
</div>
<div class="col-lg-4 col-md-6 col-sm-6">
<div class="single-gallery-item">
<a href="https://edmo.envytheme.com/draftfile.php/5/user/draft/942015966/img9.jpg" class="popup-btn">
<img src="https://edmo.envytheme.com/draftfile.php/5/user/draft/942015966/img9.jpg" alt="image">
</a>
</div>
</div>
</div>
</div>
</section>
<!-- End Gallery Area -->