Okay, so the title is just a wee bit misleading. The Unity Post Processing system has been described as Photoshop for your game. It is a way to add image processing, similar to Photoshop but apply it to everything. So, while it is indeed true a proper artist can step up the appearance of your game, someone like myself is more likely to do more damage than good. Given the level and shear number of effects one can apply at this stage, well, let’s just say it is like giving a paint brush to a horse.
But, from the images below, you can see just how much of a change you can make to the final appearance, just by turning a few knobs and flipping a couple switches.
Setting this all up was for me, almost as confusing as trying to make good use of it. Again, someone already familiar with tools like Blender will likely have not trouble with it. But for me it was a vocabulary explosion akin to learning a new language.
First and foremost, the Post Processing Unity package must be installed and enabled. Select Window -> Package Manager -> Unity Registry.
You will now see it listed in the Project tab under Packages. 
After installing the package, create an empty game object and rename it Post Process Volume. We then add a Post Proces Volume Component. Here we’ll be able to add various effects. But first, we need to check the ‘Is Global’ field. We then need to create a profile. We do this by clicking on the ‘New’ button in the Profile field. Doing so will create a folder in the Scenes tab called ‘Game_Profiles’. Under that folder will be a game object called ‘Post Process Volume Profile.’
We will also need to setup the camera. Basically, it is the camera that will deliver the effects. So, select our Main Camera and add the ‘Post Processing Layer’ component. When you do, you will see another warning. This one about no layer being assigned. Create a new layer This can be done from the Layer drop down field at the top right of the Inspector. Call the new layer ‘Post Processing’ and set that as the layer for the Volume Blending -> Layer field in the Camera -> Post-process Layer component in the Inspector. Then set this for the Post Process Volume game object in the Inspector also.
You can start adding effects such as Bloom and Color Grading to the Post Process Volume component. If you add Color Grading and want to use ‘High Definition Range’ you will need to do as the warning says.
Choose File -> Build Settings from the menu and then press the ‘Player Settings…’ button in the lower left. Then change the ‘Color Space’ setting from ‘Gamma’ to ‘Linear’.
This will cause the project to recompile. Assuming I did not miss a step, everything should be wired up now. You should be able to monkey with all the settings you can find in the Post Processing system, and they will take effect immediately.
Easy huh?