Simplest way would be to blend it with a blender or magic bullet.
What I like to do is to make the oatmeal and then mix the protein powder in. It tastes delicious and I enjoy it much more then drinking a shake.
I pour boiling water over instant quaker oats. I let it sit for around 20 minutes and then stir in the protein powder. It's awesome. You can then top it with things like fruit, chia/flax seeds, nuts etc.