Many companies create their own systems to organize and track their assets by using spreadsheets and creative filing systems.
Others invest in software that can be used to add and track their IT assets. These methods usually require a dedicated person to manage these processes.
The other option is to outsource the management of your IT assets to a third party. This option is typically delivered as a service where the provider owns the software and offers resources to help maintain and track your assets and all the associated contracts and documentation.