To activate Tone Mapping (for adjusting overall brightness) open the render Properties, (right-click on Render Scene/object) click Tone Mapping to toggle it on, then Right Click Tone Mapping icon to open Post Process Editor. Adjust Brightness and Balance to your taste. PPE will show a small visualization of the currently selected view.
Once adjusted, render as usual and after the render finishes the tone mapping will commence -hence the 'Post Process'.
The PPE is also where you would adjust flares and glows if you were to want to use them.
As an aside, one other method to preview your scene is to use the 'Scene IIR' located in the Material Editor. It's under the Sample:Sphere flyout. It will display a small, yet re-sizable preview of the fully rendered scene, (using currently selected view) including any foreground (fog, volumetrics...) or post-process shaders, shadows, etc.
The other type of IIR is Area, which displays a rendered preview of whatever area is beneath the Material Editor. Drag around the ME to various spots and the view updates for quick 'spot-checks'
These are two handy tools hidden in plain view- I don't see much talk about them but they are quite useful for testing- usually they are quicker than waiting for a full sized test render.
Hint, just like a regular render, you can press ESC key to interrupt the preview render inside the ME.
