The way a tournament ends in the TD application is 1 (or zero) players remain. You can't end it before that happens. So to end the tournament, bust all remaining players out (or leave 1).
If you're looking at how to schedule a tournament to end at around a certain time, you can use the Rounds Suggestion tool. That uses a common formula for determining the blinds that will generally force the tournament to end soon. But to be honest, it doesn't create a great schedule. You'll have to probably adjust the rounds a little bit after it's done. There are also tools on the web that can generate a schedule for you, many that are admittedly probably much better than the TD's Rounds Suggestion tool.