Front end integration

I am trying to integrate rasa into front end using the botfront ui. (GitHub - botfront/rasa-webchat: A feature-rich chat widget for Rasa and Botfront) I have a list of session_id’s in my data base which I want to use in order to work with rasa. This is relatively simple using postman etc we can specify sender id in json ie {“sender”:“value of id”}. But I cannot figure out how to specify my sender id using the socket or from front end.