To add an image on your post, go to a new line and click the "+" button on the left:
- Click the 📷 button to upload an image from your device.
- Click the 🔍 button to insert an image from Unsplash.
You can also drag and drop single or multiple images into Medium posts or copy/paste single images into a post.
To delete an image, click on it and press Delete on your keyboard (Backspace on Windows.)
Depending on the size of your image, you'll be able to test out different placement options from the toolbar.
More info: Images section.