Hi, Please advice how to add an existing module in a page to another page in the same portal and in between different portals? Thanks

To add an existing module to a new page:

Create a new page, go to the Controlpanel, click on the radio button for add existing module, in the drop-down list select the page where the module is located, then in the drop-down list below this select the name of the module that you wish to insert into the new page, click on add module

For new portals, you cannot simply copy an existing module into a new portal, the only way I can think that you may be able to achieve this is through the use of RSS feeds. So if the module on portal1 has an RSS feed, go to portal2 and you could add the newsfeed module and display the RSS feed of the module from portal1, for further information on RSS feeds have a look at:
Issue no 3