On the left-hand side of the admin menu, there is a button called “Pages”. Click on the title of a page to edit it. Pages with a dash before the title are subpages (tabs), and are displayed below the page they appear on.
Editing the Gallery: Click in between the images, then click on the pencil icon that pops up. You can type a caption into any photo, and you can click and drag photos to rearrange them. You can drag new photos from your computer onto this screen to upload new photos. Click “Update Gallery” in the bottom right when done.
Featured Image: Only tab pages need to have a featured image (the thumbnail image that shows above the tab). On the right side of the screen, under Featured Image, click “Remove Featured Image”, then click “Set featured image” and upload or select a photo of the building.