Connect your HubSpot account from the "Integrations and Apps" section of your Workspace settings, you can get there right away by clicking here:

To export one of your Publicate Newsletters just click "Export" in the editor and select Hubspot! It's as simple as that 😀

If it's not working the way you'd expect let us know and we'll do everything we can to help! The best way to do that is clicking the Chat bubble in the bottom right of the editor.