How to find Access token

Hello..

I have a query, Whenever user sends a message in the chat area, it should be automatically copied and pasted it into the UI of my app, for further process..
For that purpose, I'm using "https://api.getbase.com/v2/text_messages" API call.. (I'm not sure, Suggest me if there is any other API call is there for the above requirement)

During this Call, they are asking for ACCESS TOKEN..
And, I entered API token from the below page,
But, it is showing 401 error.. 

"details": "Required access token is missing, malformed, expired, or invalid."

 

So, Whether API token and Access token are same? And Please correct me, If I'm anywhere wrong..
Looking forward for solutions..

Thank you..