No worries, we’ve all been there, done that. 🙂 First of all the line that connects your index.html to your css file should look something like this and should go in between the
"stylesheet" type="text/css" href="styling.css">
Now, as a general rule, you should put the css file into a separate folder called css or styles just like I did in the above code sample, but leave the index.html in the root folder of your project. Hope this helps.