I think I forgot to add my charity contributions to my tax return and i just submitted it, what do I do?

If you just e-filed you will need to wait to to see if the return is rejected or accepted.   If it is rejected you can make corrections and re-file it.  If it is accepted, you will need to wait for it to be fully processed and then later you can amend to add the donations.  The donations will not have any effect unless you have enough other itemized deductions to exceed your standard deduction.