If you need a token from dialog flow, this is the way to go Access control | Dialogflow ES | Google Cloud
But, what I understand is you need to perform an action (I assume trigger a UiPath process) from dialog flow. The easier way is to to setup your application (chatbot) on UiPath and have it invoke orchestrator api using actions fulfillment if I’m not wrong.
Build fulfillment (Dialogflow) | Dialogflow and legacy Actions SDK | Google Developers
You can find orchestrator api reference and authentication on the resources below:
Using OAuth for External Apps (uipath.com)
Read me (uipath.com)