invoicing issue

Hi, 

i am not sure i have selected thr right Board but i have an issue invoicing an order to apply postage discount.

I have tried to find the invoice option within the app but apparently the app does not have this feature so i went to www.ebay.com.au 

Beside the fact that i still cannot find the option, often i ger redirected to the app when i browse the menus.

Can anybody pkease guide me step-by-step on how to find the invoicing option 

thanks

Barbara