There is a simple plugin to install ManyContacts into any joomla website:
Step 1: visit this joomla plugin page http://extensions.joomla.org/extensions/extension/contacts-and-feedback/contact-forms/manycontacts-bar
Step 1: visit this joomla plugin page http://extensions.joomla.org/extensions/extension/contacts-and-feedback/contact-forms/manycontacts-bar
Step 2: install the widget and paste your ManyContacts code