I can't find that option. It's not in edit or anywhere else that I can see.
At the moment there are no dedicated settings for adding reminders on the iOS app.
If you would like to set a reminder please follow these instructions for adding dates and times.
Basically, in the date area, enter something like "29 April at 7pm". This will have an automatic reminder for 30 minutes before due date.
Let me know if you need any more explanation.
In addition to what Brandon said, you can also create a reminder for a specific date/time manually by typing <remind today at 7pm> within the task's name.
We will consider making the option to set and manage reminders on iOS better in future updates.
I'm a new user, and I also struggled to figure out how to set a reminder within the iOS app when creating a task. I'd love to see the dedicated "add reminder" function that is available on your web app be included on the iOS app. Love the service though! Thanks!
I cannot believe that you guys haven't added this yet, and will probably cancel my premium membership due to the lack of support on this issue