WordPress comes with a built-in feature that lets you create a gallery. This feature is very basic and does not have many options, but it gets the job done.
First, you would need to edit the post or page where you want to add the image gallery. On the post edit screen, click on the ‘Add Media’ button to upload your images.
This will bring up the WordPress media uploader where you can click on ‘Select files’ button to upload your photos. You can also select photos you have previously uploaded from media library.
After uploading and selecting your images click on the create gallery link from the left column.
Next, you need to click on the ‘Create a new gallery’ button.
Media uploader will now show your selected images with gallery settings. You can add captions to each image in your gallery.
Once you are done, you can click on the ‘Insert gallery’ button.
This will close the media uploader popup, and you will be able to see your image gallery shortcode in post text editor.