connect users to tasks ?
there are several ways to answser you need.
On the first hand, this is related to the process design you have designed. We have a mechanism called actor management that you can configure in your studio. You can find the related documentation by visiting the following links:
In addition to this, a very simple example of this is described in the getting started tutorial: https://documentation.bonitasoft.com/bonita/7.9/define-who-can-do-what
Once your process is well designed, you can also change the assignment live. You can use the dedicated REST API (https://documentation.bonitasoft.com/bonita/7.9/bpm-api#toc3) or do it from the provided web portal (https://documentation.bonitasoft.com/bonita/7.9/tasks)
Hope this helps,