How to add custom css in Horizon theme?

[hooram95 (ahmad)]

@Customizing themes without an Edit code button

Sometimes, you may want to customize a Discourse theme but find that there’s no “Custom code” section with an “Edit code” button available. This often happens with remote themes (themes installed from an external source) and the preinstalled themes (Horizon & Foundation). Here’s how you can still add your customizations: Understanding the limitation For preinstalled themes, you see a banner telling you This theme is preinstalled and can not be deleted or customized For remote themes, you’ll…

Thank you so much I also face this problem but your suggestion work for me.