The operation of Certificate Transparency is specified in RFC 6962 and the submission method is specified in sections 4.1 and 4.2. A shortened version:
4.1. Add Chain to Log
POST https://<log server>/ct/v1/add-chain
4.2. Add PreCertChain to Log
POST https://<log server>/ct/v1/add-pre-chain
The format for the POST requests is specified in the beginning of section 4:
Messages are sent as HTTPS GET or POST requests. Parameters for POSTs
and all responses are encoded as JavaScript Object Notation (JSON)
objects [RFC4627].