Allow user to insert new single line text in a form?

Allow user to insert new single line text in a form?

I'm creating a simple application (contacts) but one requirement has me stumped.  Seems like it should be easy but I'm not able to come up with the right search terms to find the answer.

The requirement is to update an existing record with a brief note of when the contact was last met with and why.  The note is simple freeform text (ex. "Spoke by phone.") and the date can be a timestamp or a date field.  The date does need to be a distinct field because the user wants to be able to search by date for contact activity.

How can I enable the user to insert or add new text notes/dates to an existing record?