Most Shopify themes have a setting to adjust your logo size. This setting can be found in your Admin under Online store > Themes > Customize > Header > Custom logo width or Custom logo height. However, if you need your logo to be bigger than what this setting allows, you can follow the tutorial below.
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I wonder if you pasted the code into theme.liquid and not theme.scss.liquid? That would likely have caused the code to become visible on your website instead of making the style changes you need.
You can easily roll back liquid files individually to a time and date before you made the changes. It's also never a bad idea to keep a backup/duplicate of the file you are working on for easy reference. You can add unedited theme templates right from Admin > Online Store > Themes > Add Theme.
That should do the trick, but let me know if you have other questions.
Thanks for your comment and sharing your question.
I just had a look at your website, and it looks like your logo is already centred. Were you able to resolve this? In case I have misunderstood and you are still experiencing this issue, please grab a screenshot and share it with me here.
I look forward to your reply,
You can find theme.css.liquid file by
1> Go to the Online store
2> Click on Edit theme code
3> Open Assets folder
4> Locate theme.css.liquid file (The file can be named differently in your theme such as theme.scss.liquid or stylesheet.css.liquid etc.)
Hope that helps!
I trust that answer was helpful, @maisie-worm, but let us know if anything else comes up.