This lady messes with HTML and I am not about that life but it's helpful and not complicated and I don't think you can mess up too much by doing it, so here's the link and good luck: https://georgialoustudios.com/use-google-fonts-blogger/
If you want a little more help with DIY CSS and HTML, read this - it's interesting, helpful, and you might be able to code some stuff on your own in the future.