This part of the documentation describes the partners flow.

# Partner specific headers

All partners are required to pass their provided X-Zimpler-TechPartner ID for all transactions. The submerchant_id shall be passed in the header for collecting partners.

Header content Type Required Description
X-Zimpler-TechPartner String True PartnerID provided by Zimpler
X-Zimpler-SubMerchant String False The returned submerchant_id utilised

Kindly reach out to your Sales Manager for further information about adding submerchants.