Where do I add the picture for the blog author?

The blog author image for blog posts is pulled from the authors created in HubSpot

Open Marketing → Website → Blog and change the view to Authors:

From the Authors page, you can complete the following actions:

• Add new author
• Edit full profile
• Delete
• Create multi-language variation
• Add to a multi-language group

You can also Edit columns to show the Email and Language to make managing Authors easier: