Show images from any source : uploaded media, from your data, or by specifying a URL.
Uploaded Media
You can add media to your project library using the + at the top right and following the prompts, though this should usually just be for one-off, hero and featured images.
Dynamic
Wheny you have a data source, such as a user or a repeating components and you want to show images - just switch to dynamic mode and you can choose any variables / fields that contain images.