One of the sections within the Know Your Client area of contact overviews is the Health Information section, accessible by clicking the "Misc Client Info" tab at the top of this section:
To add or edit any information here, click the Edit button in the top right corner of the section. You'd then see the below:
All of the fields here (other than the Is Smoker? checkbox) are free form fields. To indicate a contact is a smoker, just check off the box.
This area might look similar to our original example above once you've added your desired information.