When you work with hubsell sourced data the salutation is already part of the delivered prospects, the process is to just type the placeholder {{salutation}}.
However, If you are working with imported data you have to define either gender or salutation manually. If you have already defined the salutation manually, you can simply use the placeholder {{salutation}}.
If however, you have only defined the gender of your imported contacts, please take the following steps:
Go to campaigns
Choose the campaign
Click the stat button to switch to edit mode
Go to the email point and edit
Type a curly bracket '{' to open the formula helper
Click if statement > gender > equals > male
Please repeat the same process for adding the female gender
By clicking add condition > gender > equals > female > finish
Don't forget to click save changes.