In the Emailify export panel, select the HubSpot option from the dropdown list, then paste in a valid HubSpot Private App API key, which can be generated from your HubSpot account by creating a new Private App from the Integrations -> Private Apps page in your HubSpot account settings by following then steps below:

1. Click the Create private app button
2. On the Basic Info tab, give the private a name (eg. Emailify)
3. Then on the Scopes tab, search for content and tick the content checkbox.
4. Click the Create app button, then click Continue creating
5. Click the Show token button, then click the Copy button
6. Store this key somewhere safe (for future re-use/reference)
7. Go back to Emailify and paste it in the HubSpot API key input

When you're ready, click the Upload To HubSpot button to start exporting the emails you've selected from Figma to HTML, and have them automatically be uploaded to your HubSpot templates.