depending on your grow space you'll want to move your plants into 3 or 5 gallon containers. how much vertical room do you have? what strain are your plants?
all you have to do is remove your plant from it's container and put it into the larger container with the appropriate amount of medium to fill it up. if the plant is rootbound, i like to cut off the last half inch of roots to get them growing again. someone may disagree with that practice but it always works for me.
after you transplant, make sure you get your babies a decent watering. they should be fine in a few days. if you see some drooping or yellowing, have no fear, it's just the plant adjusting to it's new environment.