Hi Friends,
I want to add this css style to existing template.

.citems {
    font-family: 'Open Sans', sans-serif;
    font-size: 14px;
    color: #000;
    line-height: 20px;
    border-bottom-width: thin;
    border-top-style: none;
    border-right-style: none;
    border-bottom-style: dotted;
    border-left-style: none;
    border-top-color: #000;
    border-right-color: #000;
    border-bottom-color: #333;
    border-left-color: #000;
    text-indent: 10px;
}



@font-face {
  font-family: 'Open Sans';
  font-style: normal;
  font-weight: 400;
  src: local('Open Sans'), local('OpenSans'), url(http://themes.googleusercontent.com/static/fonts/opensans/v8/cJZKeOuBrn4kERxqtaUH3T8E0i7KZn-EPnyo3HZu7kw.woff) format('woff');

How can I do this?
Are there any plugin or should I link new style sheet.
If so, how can I link new style sheet?

Hola,

There are multiple ways to do this:

1) You can use custom code modules/plugins like:
http://extensions.joomla.org/extensions/core-enhancements/coding-a-scripts-integration/custom-code-in-modules/3668

Or

http://extensions.joomla.org/extensions/core-enhancements/coding-a-scripts-integration/custom-code-in-modules/15251

These modules give you a blank space to write your own css or html code. Now you can publish them in debug position (& choose which pages/menu items you want effected by this css code).

2) If you wish to have the css code added to the template directly, look for the style.css (mostly named this in most templates) and your css code.

If you can tell us what template you are using we can help you more :)