API details to add custom activities data

Business requirement is to create Custom Activities table and add the additional activity details captured on third party tool using REST API. I have created custom object activities table but did not find Marketo Endpoint reference details  to add the activities data in the table. I found below link but it 's not containing any parameter in URL path. Hence, I was wondering how can it will insert into the custom activity table without API reference given for the particular custom activity table  

https://developers.marketo.com/rest-api/endpoint-reference/lead-database-endpoint-reference/#/