How do i disconnect the battery in my mondeo?

I need to disconnect the battery in my 1.8 zetec mondeo, as it was misfiring and i read that it can be a common fault with these mondeos for the ECU to think it is still misfiring after it has actually been fixed. So, I need to disconnect the battery to wipe the ECU memory i think and am pretty clueless on what to do, a) because i'm female and b) because I have basic knowledge of cars as nobody ever taught me! So please help, this issue is getting annoying!