Creating Custom Fields allows for a greater range of visibility as well as allowing you to suit your business and project needs.
*NOTE* Custom Field Tables, Sorting, and Filtering by Custom Fields is not yet available, but will be in the future. Any fields you create now will only be available in contact and company profiles.
*NOTE* To create Custom Fields, you need Admin level permissions in your account.
To start select "Account" in the bottom left of your screen then select "Account Settings"
Next select "Customizations" then "Custom Contact Field" or "Custom Company Field"
In the top right corner of the screen you will see "Add Custom Company/Contact Field". Select the option and it will open the field creator.
The Field creator allows you to name the Field, create a description of what the Field is and the Field type.
Once the field has been created you can add it under the contact/company by navigating to the contact/company profile. Once the profile has been located click the three dots above the contacts/company profile picture then select "Edit".
Inside of the editor scroll down the page, toward the bottom you will see your custom field options.
Once the Fields have been filled out on the Contact/Company profile you will be able to see the Fields under "About the Contact/Company"