Linking Invoices to spread sheet

[Ollie238]

Hi I'm not brilliant with computers but can do a little bit. Was hoping that someone could help me. I have an excel invoice template that a friend has made me. (Trying to make myself a bit more professional). I want to link the total from every invoice i produce to another spread sheet so i have a total of my incoming. I have done a bit with excel but just basics. I am hoping someone can explain how to do this in layman terms please. Many thanks Ollie