How to set Task Owner from BPM Worklist?

Summary:

We would like to be able to set the owner based on username or Role from BPM

Content (please ensure you mask any confidential information):

Hi, we are trying to configure the owner of the task (Change Location) based on Role or User.

We put the username of an HR after clicking on the taskownerUser but nothing changed. How does this actually work? Is there a specific language to use in this page?

Thanks, Giuseppe