Get a job doing HR Application support, assisting with applications like Applicant Tracking Systems, metrics and reporting systems, etc. Those systems, in large companies, are often integrated with SAP and you'll begin to be in contact and learn about SAP as you deal with isues arising from the integrations.
The HR AS (Application Support) analyst I work with is transitioning off to the SAP team now.
<---- in Recruiting, admins an applicant tracking system