From the editor, click on the image icon
Next, click on the search icon in the Source field like so:
3. You'll see a pop-up like this:
4. Click on 'Upload a photo' and add your photo in.
❗ Please note that this upload function is only available inside the Email Template builder. You will not be able to do this when sending out an email itself.
5. If your image is uploaded properly, you'll see that the source field is updated like so:
6. Click on 'OK' and you should see your image in the editor.
7. To resize the image, click on the image and use the image controls simply by dragging to the size you want it to be:
Alternatively, you could use the Dimensions field for precise sizing.
Select the 'Constrain propositions' checkbox to resize proportionately.