The first time you choose a Pro plan, a 7-day free trial starts automatically (card needed; nothing is charged until it ends) — no need to do anything extra to activate it. Just know it's a one-time thing per account, so a later resubscription won't include a second trial.
Trying Pro with a free trial
The first time you choose a Pro plan, a 7-day free trial starts automatically (card needed; nothing is charged until it ends) — no need to do anything extra to activate it.