Bloom

Setup

In the project window, right click and select Create/Toon RP/Post-Processing/Bloom.
Go to your pipeline asset, make sure the post-processing is enabled, and add the newly created asset to the Post-Processing Passes list.

Bloom

Bloom detects bright areas of a picture and blurs their edges.

Parameters:

Intensity: controls the overall power of the effect;
Threshold: a minimum luminance for bloom to apply;
Threshold Knee: smoothness of the bloom threshold;
Max Iterations: bloom performs blurring in several steps, each of them halves the resolution. Reducing it to a low value like 4 improves performance but can also cause flickering artifacts.
Resolution Factor: reduces the resolution used for the overall effect;
Downsample Limit: minimum texture size for blur steps;
Pattern: applies a stylized (dotted) pattern to the bloom result.