With the old version of post processing which I believe is still up on the asset store you right click in the project panel and select "Post Processing Profile" or something along those lines. In Unity 2018 you can use the Lightweight or High Definition Render pipeline which has post processing built in.
With those templates used, you'd create a post processing layer on the camera (add component), then create a separate game object and apply the post processing volume set to global and from there you can add individual post processing effects through that volume. You'll have the option to create a profile on the volume component.
