Personalising header with logo

I am a complete novice and have recently set up my personal blog https://icywriter.co.nf I am trying to customise it so I installed the Cherry Blossom theme and I love the image so all I want to do now is add a tailored logo containing my site name and a symbol to it but I am at a loss as how to do that if it’s even possible. Any help and advice would be most appreciated as I am learning as I go. Thanks in advance.