claim and verify your profile
Before anything else, claim and verify the profile through Google. An unverified profile can't be fully optimized, can't respond to reviews, and can't post. Verification usually takes a few days via postcard, phone, or video depending on the business type.
If a duplicate or competitor-edited profile exists, request merging or suppression through Google before you start optimizing — optimizing two competing profiles splits your authority and confuses the ranking signal.
