Chaos Cosmos Browser is launched from within your Chaos product (e.g., from the V-Ray Toolbar or V-Ray Menu). Once launched, you can browse through the various categories of 3D models to pick your desired asset with many sorting options.
Cosmos also has a search function where you can search on asset characteristics such as object type, color, publisher, etc.
For more product-specific information on the steps, please visit Chaos Cosmos documentation section.