Smart Compose for Google Docs is out of beta, but it's not yet mainstream
If you have a G Suite account, you should notice the new feature when you're writing something in Google Docs. The search giant announced the rollout started a week ago but said it may take up to 15 days for everyone to see it on their devices.
You don't have to do anything to enable it since Smart Compose will be ON by default, but you can disable it if you want by heading to Tools / Preferences and unchecking “Show Smart Compose Suggestions.”
Keep in mind that Smart Compose for Google Docs is not available to users with personal Google Accounts or those with G Suite for Education, G Suite Enterprise for Education and G Suite for Nonprofits. You can only get it if you're a G Suite Basic, G Suite Business, or G Suite Enterprise customer.