How to Insert First name property into emails

Hi there @ayor!

Welcome to the Community and Happy New Year!
I believe you’re looking for this code to dynamically populate the First Name into your emails: {{ first_name|default:'' }} In order for Klaviyo to display the first name of your subscriber in the email, you must have that information for your subscriber. Usually, many community members have subscribers with the first name information and subscribers for which they only have their email address. I assume this is your case too. Subscribers that you have in your account that have the first name information are usually customers who came into Klaviyo by purchasing something in your store or from filling out a form that collects this data. 
On the other hand, if the subscriber comes through a form (pop-up for example) that only requires him to enter his email address, you haven’t captured his first name. If you don’t have the first name of your subscriber, Klaviyo can’t know what to put there.
This is why the code {{ first_name|default:'' }} contains the |default:'' part.
Between the brackets in that part, you can put something generic that will be used for subscribers without the first name information.
Example:
Hi {{ first_name|default:'there' }}!
For a subscriber (E.g. Alex) that you have the first name information it will display:
Hi Alex!
For a subscriber that you don’t have the first name information it will display:
Hi there!

We have a great document regarding template tags and dynamic syntax that I would highly recommend checking out too!
Have a good day,

Alex