This post assumes you’ve already created your gallery.
1. On the page or post you want to add the gallery, click in the text area where you want your gallery to appear.
2. In the toolbar, click the green box to add NextGen Gallery.
3. From the pop-up window, in the Display Galleries tab, select the display type, such as NextGen Pro Slideshow.
4. Click the “What would you like to display” menu. From the “Sources” menu, choose Galleries. From the “Galleries” menu, choose which gallery you want to display.
5. If you wish to customize the display, click the “Customize the display settings” menu and customize as you want. I typically leave this alone.
6. From the “Sort or Exclude Images” menu, I normally don’t change anything.
7. Click Save.
8. Click Update or Publish.