Change Navigation Font – Shopkeeper Theme

Hello!

I recently bought the Shopkeeper theme and what i want to do is to change fonts in the Main Navigation Menu. I’ve been in contact with the creators of this theme and they have told me that there are no built-in option that can let you change the navigation font, so what i have to do is to use the Custom Code function.

They sadly cannot help me with this, and tell me what kind of codes it is that i should put in there, because it falls outside their support policy.

I need help from someone who can tell me what codes it is that i should use in Custom Code, so the Main Navigation Menu changes fonts.. I would be very grateful if someone could help me out!

This is how it looks like, where i should put in the Custom Code:
http://i.imgur.com/Wj9veJ2.png?1