How do I remove the Site Title from my Website???

Hi there, this is my first website and I have very little idea what I’m doing which is proving to be incredibly frustrating! I am using the Coeur theme and trying to remove the site title displayed in the header of my site without simply deleting it in settings>site title.

I have tried inputting this into my CSS editor, to no avail:

#site-title {
display:none;
}

Please help! It’s driving me c r a z y and I really would like to launch my site soon.

Thank you in advance!

Alessia