In this section of your cover letter, you will typically greet your recipient by name, followed by a colon.
In most cases, use the recipient's prefix and last name (i.e., Dear Ms. Doe). But you can adjust this to reflect your relationship with the recipient. If you are on a first-name basis, for example, you could greet the recipient with: "Dear Jane" instead of the more formal alternative.
View the full-size version of the cover letter example shown here.