Replace the text with following code. If there is no translation available, the second parameter will be used instead. So it should be in english.
plugin:
SWFM.i18n.get('plugin.plugin_name', 'Text to translate')
widget:
SWFM.i18n.get('widget.plugin_name', 'Text to translate')
Translations are located in the locale/ folders. There is a general folder for SmartWFM core tranlations in swfm/locale and each plugin or widget has such a folder (swfm/plugins/PLUGIN_NAME/locale/, swfm/widgets/WIDGET_NAME/locale/).
Translation files in these folders are named by a (two-lettered) language code like the IETF language tag. In example en for English or es for Spanish. So these files are named en.js or es.js.
The needed files are automatically loaded by the SmartWFM core. So other translations or translations of not used plugins/widgets will not be loaded.
Typically there are two sections of translations ordinary text and error messages:
SmartWFM.I18N.add('es', 'plugin.plugin_name', {
'text to translate 1': 'translation 1',
'text to translate 2': 'translation 2'
});
SmartWFM.I18N.add('es', 'plugin.plugin_name.error', {
'error message to translate 1': 'error translation 1',
'error message to translate 2': 'error translation 2'
});