Audits run scheduled rank checks for a location against its competitors. In MLAP Settings > Audits you choose which audit configs feed into MLAP.
Each location lists its audit configs. Enable a config to count its audit data in MLAP, or disable it to pause without losing history. Each config runs automatically on its own schedule (weekly, monthly, and so on) and compares your visibility against the competitors defined on it.
For setting up the audits themselves, see Audit Configurations.