I looked all through their support and couldn't find this.
Does anyone have the corrrect postback setup for
Have you tried the following? 
https://trc.taboola.com/actions-handler/log/3/s2s-action?click-id={externalid}&partner-name=YOURPARTNERNAME
Thanks for that. I get this part clickid={externalid}
However, what do you put in the externalid palceholder and parameter?
Also not sure what you mean by "yourpartnername"
If this is the postback for taboola - https://trc.taboola.com/actions-handler/log/3/s2s-action?click-id={externalid}&partner-name=YOURPARTNERNAME
Does anyone know what the placeholder is for "click-id" for taboola. Please see image attached.
Any help is much appreciated.