Integrating with Every Action (CRM)?

I need to integrate with our CRM (Every Action) to do the following:

• Create contacts and add them to newsletters in EA
• Create petition and fundraising campaigns in EA, based on users/contact
• Sync petition signatures and donations with campaigns in the EA
• Send email to representatives via EA when a signature occurs

EA provides a RESTful API, but I don’t know how to create RESTful endpoints in WP without ACF or something similar. Any advice would be appreciated.