A Gallery can be added to a default notice by following the steps below.
Click the 'Add Media' Button
2. Next click the 'Create Gallery' button on the left panel
3. Then, select the images you would like to include in the gallery
4. Once all required images are selected, click the 'Create a new gallery' button
5. Finally, click the 'Insert Gallery' button
That's it! You have successfully added a gallery to your notice.