It will do it automatically if the return reflects some form of SE income.

Following the IRS scheme, "Schedules" are part of "Forms." Are you working on a Form 1040 for someone who has self-employment activities? Did you enter their info?

Yes, I'm helping a client with self-employment. I'm working on schedule C, but my question is if I have to check the box "All income subject to SE tax"? Because I finished schedule C and I don't see any schedule SE. 

"if I have to check the box "All income subject to SE tax"?'

You have to do whatever applies, for everything. Is that income subject to SE or not? No one on the internet can answer this question.

The IRS has interactive tax assistants (wizards). Follow this one:

https://www.irs.gov/help/ita/do-i-have-income-subject-to-self-employment-tax

Does his/her Sch C show a profit?

AND, if so, are you sure the SE tax isn't showing up somewhere else on the F 1040 other than on the Sch C?