Has anyone converted their community's resident parking from free to paid before

Has anyone converted their community's resident parking from free to paid before?
Any good lessons in doing that? Mistakes you made, communication tips, etc?

Highly recommend you do this with your renewals and with a very long lead up time. People will be angry and their current agreements don't include having to pay for parking.
We had to do this when we went no smoking. 90 days notice before new leases and renewals would start requiring no smoking. Every renewal becomes beholden to the new rules. Every new rental has this in the lease and are notified that this is a transisiton. Month to month folks had to sign a separate addendum. Constant communication was put out. Signs all over the property for when it would start and be enforced.
Make sure there is a reminder that this will be on the new renewals and parking enforcement will begin. Make sure all new tenants are aware of the transision and to follow their lease. Even if older residents say otherwise. Set a date a year from your last "old" lease for when this will be complete.
Do it through the lease agreement. Protect yourself legally. Protect your reviews. Give your resident time to decide if this new rule is where they want to be. It's a long process but it's worth taking time.

My best advice is communicate a lot in advance and do not be too lenient when people violate. If you prepare them well before the transition and they are fully informed, they will know what to expect and (hopefully) will not give your team too much of a hard time.