Here’s how to add new photos to a Page or Post which displays an existing Gallery within WordPress.
1. Upload the new images
If your post or page already contains a gallery, you’ll see an image like this within the WordPress editing box:-
To add a new photo, you can just click on the WordPress Upload/Insert icon just above the text entry box.
Then browse to the location of the file(s) on your computer and upload.
2. Close the media box and Update your post/page
You don’t need to click on Insert into Post (which will insert a full size picture into the post, rather than the thumbnail). Just the act of uploading an image while editing this page/post will associate that image with the page and it will then appear in the gallery when the page is displayed.
After uploading your image(s) you can just close the Media box. Remember to Update your post/page when you are finished.
1. Edit the gallery
Click on the gallery image with the editing box. You’ll see two little icons – the Edit Gallery and Delete Gallery icons.
2. Add new images, edit or delete images within the Media box
Click on the Edit Gallery icon to see the Media box, open at the Gallery tab and showing a list of the images in this gallery. You can edit the Titles, Alt text or the way the gallery is displayed, from within this tab. You can even delete unwanted pictures by clicking on Show and then Delete (near the bottom of the information for that picture).
Remember to click on Save Changes and/or Update Gallery before leaving the Media box.
To add a new photo, click on the From Computer tab and then upload the new photo(s) in the usual way. Again, make sure you don’t click on Insert into Post (which will insert a full size picture into the post, rather than the thumbnail). Just the act of uploading an image while editing this page will associate that image with this page and therefore its gallery.
3. Close the media box and Update your post/page
After uploading your image(s) you can just close the Media box.
And remember to Update your post/page when you are finished.