i personally cut the top of the bag off and pour the shrimp into the fish net then run the shrimp in the net under tap water for a little bit, then put the shrimp in the aquarium and watch the fish gobble them all up.
Shrimp are cultivated in salt water which is why i wash them off in tap water, you have less risk in introducing disease into your aquarium by not pouring the water from the bag in with them.
hope this helps
Scott