Here are the conversation (a quote from The Marvelous Mrs.Masel)
The two characters are preparing for a car to travel, and A is clearing up the backseat of the car.
A: This car is unkempt, to say the least.
B: Hey, lady, I could use another hand.
A: I have to make sure nothing back here gets crushed and wrinkled.
What's the meaning of "I could use another hand"?