An Inbound Mapping reference is required to make requests to the PUT Record API, all your mapping references can be found in Data → Rest APIs → Inbound Mapping.
Setting New Inbound Mapping
1. Go to Data → Rest APIs.
2. Select Inbound Mapping in the menu.
3. Click on +New Mapping button.
4. On Data type choose the relevant Data Type for your integration and fill the Configuration name field.
5. On Field Mapping choose all the fields you want to import into the system and their Field Heading.
6. Click on the Save button to finish the mapping creation.