Go to ePO console > Menu > User Management > Audit log.
Navigate to Actions (bottom left side on screen) and select Purge.
Put 0 Days under Purge records older than and click OK.
Logs will be gone.
I advise from clearing your ePO audit logs if A) you don't send your epo Audit Logs to a SIEM and B) are required to meet DOD/Federal complaince regulations IE NIST 800-53. Depending on your regulatory requirements, deleting the ePO Audit log can lead to your firing or even having to hire a lawyer.