How to add custom css in wix website

You can do this by embedding inline styles to every page, via creating a chunk of custom css code contained between <style> and </style>.

1. Go to your site's dashboard.
2. Click Manage Website on the left.
3. Click Tracking & Analytics.
4. Click + New Tool **and select **Custom from the dropdown.
5. Set up your custom code:
   1. Enter your custom code.
   2. Select the relevant domain. Note: This option will appear only if you have multiple domains.
   3. Enter a name for your custom code.
   4. Add Code to Pages: Select which pages to add your code to:
      • **All Pages: **Click the dropdown to select an option:
        • Load code once.
        • Load code on each new page.
      • **Choose specific pages: **Begin typing the name of the relevant pages and then click the checkbox next to the relevant page.
   5. Place Code in: Select where the code snippet in placed in your site's code:
      • Head - as noted by @Daniel Gurtner, avoid this because it'll insert it BEFORE any of the inherent styles, which makes it mostly useless here.
      • Body - start
      • Body - end Note: I'd recommend adding your style chunk here to avoid having a delay effect on your loading
6. Click Apply.

Wix keeps on updating this but I have found where the place described in the most voted comment is for now. I don't have enough "reputation" to add a comment to the thread, hence why this is an answer.

Go to Settings and scroll to Advanced(the last section) and you can see Custom Code. The rest of the steps are the same.