Adding image to header

Hi,

I’m new at WordPress and I’ve just managed to install it on my host. I am working to edit the theme a litte and would like to add my own logo in the header. Can anyone advise me on how to do this?
The theme I’m using is ‘Buddymatic’ and this is my site at the moment: http://www.jecreative.net.

I’m not completely code clueless but I’m an html and css kind of person! Don’t know much about .php.

Could anyone give any advice please?

Thanks!
Jenny