Using OTDS Impersonation REST API

Hi
I am developing a solution where I need to Impersonate users in eDOCS.
eDOCS is set up as a Resource in OTDS.
I tried the API call "/authentication/ticketforuser" and I got a ticket for a specific user. When I try to use that ticket as "X-DM-DTS" in the header when calling eDOCS REST API I get "No Security Token has been Set".
Should I use "/authentication/resource/ticketforuser"?
If so, how do I use it?
I can not figure out what the "secureSecret/authenticator" is.

OTDS API reference:
https://developer.opentext.com/webaccess/#url=%2Fawd%2Fresources%2Fapis%2Fotds-16%23!%2Fauthentication%2FresourceRequestTicketForUser_post_5&tab=501

regards
Peter