History is accessible by accessing your camera in the Google Home app (and selecting History / Full History) or in the Google Nest app (and scrolling through the timeline). Which app you use depends on which camera you have. What history (if any) you see depends on what Nest Aware subscription you have (free 30-day trial, Nest Aware, or Nest Aware Plus). The newer Google Nest cameras provide event history for just the most recent 3 hours without a subscription.
(If you want to contact Google Nest Support, use the "Contact us" option on either of those pages.)