Ancestry visa ($15 return postage) EMERGENCY!!

so I finally went through all the hoopla and have a date set for me to take my biometrics (one week from tofay). I have been reading this forum for months and it has been priceless so thx to everyone.

One thing I remember reading over and over was when paying to ensure that I add $15 return postage. Today when I was paying NOWHERE did I find any option to pay $15 for return postage?

What do I do?
Have I just destroyed any chance I have of getting the original documents back? If so my family are going to kill me.

Any help would be greatly appreciated

thx

Guy freakin out