Opening first sub-item when accordion header clicked

Hi,

I was hoping someone may be able to provide me with some guidance in achieving the following.

Accordion Header 1
-- sub item 1
-- sub item 2
-- sub item 3

Accordion Header 2
-- sub item 1
-- sub item 2
-- sub item 3

I am trying to have it so that when an accordion header is clicked, the accordion sections opens and the first item (in this case sub item 1) is automatically loaded.

If I was to click Accordion Header 2, it would open that section and load in its sub item 1 automatically.

Thanks in advance for any assistance
Gregg