You would use the expression d'accord when you agree with something. For example: Oui, je suis <u>d'accord </u>avec vous. - Yes, I <u>agree </u>with you. It can also translate as sure, okay, of course, naturally, alright, etc.
May be its just me but i think the simplest is the best: tell 'em that u know u screwed up but u are asking 4 a 2nd chance and u will be responsible now.