I am frustrated in trying to set an automatic outdoor watering timer for several flower pots. I need it to operate twice daily, but can only get it to come on once. Can you instruct me on what I am doing wrong?

They're all a bit different. What is the make and model number of your timing device(s)?

Will have to get that info

Melnor Electronic Aqua Timer Model 3060

Need help to properly set the above system to water flower pots twice daily. Can only get it to turn on once a day.

Here's a link to their instruction Manuals:
Melnor - Instructions

Which of these models is yours?