How to add Photos to a Gallery that has been published already
Step 1: To add photos to an existing gallery, hover over the gallery that you would like to update and click on the 'Edit' button.
Step 2: Click into the Content box of your gallery, you should see a pencil icon appear, then click on that pencil icon.
Step 3: On the left hand side of the screen, click on the 'Add to Gallery' button.
Step 4: Select the photos from your media library that you would like to add to your photo gallery or click on the 'Upload Files' tab that sits next to the 'Media Library' tab if you need to upload photos directly from your computer.
Step 5: When you are finished selecting your media, click on the 'Add to Gallery' button in the bottom right hand corner.
Step 6: You can add captions and reorganize the order of your photos on this screen. When you are finished click on the 'update Gallery' button.
Step 7: If you feel that you are happy with how your gallery looks, go ahead and click on the blue 'Update' button on the far right hand side in the 'Publish' widget.
Now your updated gallery is live!