You'll find over time that your periods develop a pattern. For example, heavy for the first two days (needing constant, maximum coverage) and then a moderate flow for 2 days and then spotty after that. If you get to the point where it is spotty, you can use lighter pads. You'll figure it out.
I believe that on your first days Atleast u should wear pads all day but once it's starting to get lighter as the days go by, you can start wearing panty liners less and less
Don't worry you'll soon get used to it. :)
Unless your flow is really light and can wear panty liners its best to wear pads all day and night (change when necessary)