To enable the audit log by using Central Administration:

  • On the Central Administration home page, in the Application Management section, click Manage service applications.
  • Select the Secure Store service application.
  • On the ribbon, click Properties.
  • From the Enable Audit section, click to select the Audit log enabled box.
  • To change the number of days that entries will be purged from the audit log file, specify a number in days in the Days until Purge field.
  • The default value is 30 days.
  • Click OK.

Configure audit settings for a site collection


Please use the following link in which Microsoft has given a very detailed description that references each and every minor point regarding audit settings:

It consists of:
  • Auditing event information
  • Trimming the audit logs (new enhancements in SP2010 and SP2013 as compare to earlier versions)
  • Configure audit log trimming
  • Configure events to audit

MS Reference

http://office.microsoft.com/en-us/sharepoint-help/configure-audit-settings-for-a-site-collection-HA102866204.aspx

View audit log reports

The following link will help you understand the following points:
  • Events available for audit log reports
  • Available audit log reports
  • View audit log reports

MS Reference

http://office.microsoft.com/en-us/sharepoint-help/view-audit-log-reports-HA102772739.aspx

See Also

  1. SharePoint Resources on the TechNet Wiki
  2. SharePoint 2013 Portal
  3. SharePoint 2013 - Service Applications
  4. SharePoint 2013 - Resources for Developers
  5. SharePoint 2013 - Resources for IT Pros