How do I add Affected User to Call and Incident Form?

[APadgett]

When I try to add Affected User field to Incident form, it does not appear as an available option to add to the form. 

I have checked Yes for 

Allow base table lists (task, cmdb_ci, etc.) to include extended table fields (incident_state, os_version, etc.), and allow filtering on extended table fields.

[APadgett]

1. I created a new field in Configure Call Form
2. Name: Affected User
3. Type: Reference
4. Table to Reference: sys_user
5. Clicked Add.

This created the field I need. Though I do not believe this is the right way to do it and that Affected User has to be an OOB field in some version of ServiceNow or it would not have so many references in the community posts. 

Thanks everyone, now I am trying to figure out why the Caller field set to Mandatory only flashes the Red Asterisk next to the field name, then the asterisk disappears.

[Jan Cernocky]

Keep in mind that it's not a best practice to create a new field with similar function. Do I understand well that you now have a field caller which is not used at all and have a new one (most likely) u_affected_user that has the similar function? From my point of view it is definitely better to reuse what is there and adjust the name or behavior (mandatory/read-only/). I've been with SNOW since Istanbul and do not recall any field called "affected user".

How did you mean that with the asterisk? It's there and red if the field is mandatory, it's there but gray if the mandatory field has a value. You can either set this up to have static behavior by configuring dictionary or dynamic behavior based on UI policy or UI script (usually change behavior based on a value of this field or another field)