Although the People® system brands it's SAML provider as being OneLogin - the mechanism used is compatible with all SAML identity providers. Please find all links to all detailed instructions on how to implement different providers.
WS02 - http://help.peoplehr.com/integrations/single-sign-on-sso/configure-sso-ws02
Okta / Ping Identity -
You can use instructions for OneLogin however just replace the instructions that show how to produce the XML file from OneLogin with the production of the XML file from your Identity provider.
SSO communication process
When a user selects the Single Sign On option from the login screen, the
People® application will communicate with the identity provider.
This communication will be done by sending the SAML data in an encrypted
base64string. The request will always be sent as a POST request.
Customer Services Team