Short answer
HubSpot's KB: turn the company sync on before importing Salesforce accounts, or companies won't be created. After that, new accounts are created as companies automatically. A contact's lifecycle stage change syncs to the company's lifecycle stage.
1. In HubSpot
The relevant screen in my demo portal.

2. Worth knowing
Review sync rules for edits made in Salesforce.
3. Related
Integration settings and sync rules.