If you wish to customize the stylesheets being used by the portal, you may do so using the Admin Toolbar. Here is a quick overview:

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I. Edit/Add Classes in Existing Style Sheet

You can add new classes or edit existing classes using the Style Sheet editor.
  From the Admin Toolbar, select Style Sheet under the Site menu.


  From here you are free to edit all classes.


  Please refer to W3 Schools for a detailed overview of the CSS Language.

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II. Add a stylesheet to the template

If you have a completed stylesheet you want to link to, you can add it in the Template editor.
  From the Admin Toolbar, select the template you are using from the Edit Layouts menu under the Site menu.


  Add the following line of code in the blank space below the other "link" tag.
  <link href="main.css" rel="stylesheet" type="text/css" />


  Change main.css to the name and location of your style sheet.