How to add custom language specified text?
You can set the translations for each specified language in the strings settings part of the internationalization module: /admin/config/regional/i18n_translation

To show it in a template file you simply use the t() function to wrap your text - which translates text for you and automatically adds new text defined in the t() function to the strings page. 

See http://api.drupal.org/api/drupal/includes--bootstrap.inc/function/t/7

If you are hardcoding links with your text you can use l(), so if you have say a text link and want the text to be translated you would use l() and in it define your text using t() - something like this:  http://api.drupal.org/api/drupal/includes--bootstrap.inc/function/t/7

See http://api.drupal.org/api/drupal/includes--common.inc/function/l/7 for its usage.