If the existing fields are not enough for you to record client data, create your own. You can add them to all types of records and it's up to you what they will look like. They can be set up in the form of a text box, a drop-down list, a checkbox, and more. Create new fields in
Settings - Record Settings - Select the record type - Field settings - Add custom field - Create new field. Detailed instructions can be found
here, or check out the short video version here.