Deltoids is essentially the anterior deltoids, so the front of your shoulder.

You extend your arm in front of you and then you cross it over making sure that your elbows are in line with your shoulders.

And just hold it behind there. You should fill your interior deltoids the front of your shoulders.

You can go down on the floor onto a square position like a cat position.

Cross one arm under, thread in the middle, bringing the shoulder to the floor and looking at the opposite direction.