Solved: How to generate a value out of my own certain inputs

I am new to mockaroo. And one of my usage case is: I need a field to generate a value out of some certain values.
For example: the possible selection is Android, iOS, Windows. And for this field, each data is just one of the three.
How to define this usage?
Thank you
Chris Bao

Edited:
I noticed the regular expression function, which can solve my problem.

For the Android platform, you have a lot of simulators which you can get from https://uaetechnician.ae/samsung-service-centre and you can also get assistance.