If you have a full Among Us account (AKA are above the age of digital consent within your country) OR a child account with parental permission, then you can easily change your chat settings! Players on temporary accounts due to not being able to fully log into the game cannot use Free Chat!
When hosting a game or searching for a game to join, you can filter games by toggling between Free or Quick Chat or Quick Chat Only
If you are unable to toggle these options, then that means you are either not logged in (and thus on a temporary account) or you do not have parental permission to access Free Chat. Please fill out a Support Ticket for this account issue if you're still having trouble. Please know that we cannot grant you parental permission and that if you are on a child account you will have to go through Kids Web Services' process in order to enable Free Chat.
You can find out more about Kids Web Services's age verification process here.