I am not sure you can.
I stand to be corrected, but...the way I understood how Collector works, is as the device signs into the system (Portal / AGOL) and downloads the shared data, the device is assigned a unique ID.
This ID changes (as in you can log in and download data multiple times and each time the device will get a new ID. It is therefore difficult to use the "Created User" for the databases / information collected through the Collected App.
I think those "Created By" and "Edited By" fields would work in a situation with many users running ESRI products / database versions across a network / desktop environment. Where a user would physically log into and access the data directly.
Edit - Update below:
A work around I used to used to track what information was captured by which field worker was the following:
- Create a "User" field in the feature being captured (before publishing the data / service)...if you can have this as the first field in the feature.
- Create a domain, listing the field workers' names / codes / identifier you plan to use and attach that domain to the field you created in 1. You could also make this field compulsory / mandatory by making this field "un-nullable"...
- Publish the service as per normal. The field worker, when initiating the capture, has to choose their name from the dropdowns. If you made the field compulsory, then they cannot submit the data until they have placed their details in the field.
This does require some trust on your part that the field worker is doing their job. I have in some cases added a "track log" to the Collector as an invisible feature, which captures information at a given interval. This can be used to corroborate the information collected by time, date and location. But...in a perfect world where everyone does what they are paid to do, you shouldnt have to worry about things like that.