Adding a link to an image
Adding a link to an image will depend on the editor you're using.
Drag and drop editor
Click on your image, and on the left side panel, you can insert your URL in the Link section:

Code your own editor
You can edit the link added to the image in the Code your own editor by editing the HTML of the email.
We offer two kinds of editors – Drag and drop and Code your own. For most users, we recommend using our Drag and drop editor. It's simpler to use and ensure your email looks good across email clients.