Keeping fingers crossed is something that we do to get good luck. When a person tells me he has his fingers crossed for you it means he is hoping and praying that you will get your wish come true, that the thing you want will happen. "I will keep my fingers crossed" means I wish you good luck and hope you will be successful.

keep the fingers crossed = to pray ( in Western culture ). The meaning is " I sincerely hope you will soon receive good news from ...."

keep your fingers crossed -> to hope strongly that something will happen