There are two ways to add an image to a page.
Add a cover image
A cover image is a great way to add personality and showcase your branding in the hub. You can add a different cover image to each page if you like. You'll find a shortcut under the page title, and it also appears under the Options menu.
The recommended size: 1152px × 400px and you can drag and drop or click to browse for a file.
Drag and drop
If you wish to add an image to your page somewhere other than at the top, you can click to add a text block and then drag and drop an image into the block. It should be noted that this method does not enable you to fine-tune the sizing or placement in-app, nor add alt text. In the future, we'll be looking to add file uploads to pages, but this is a workaround for the short term.