TOPIC:

I have download the Greek language package from JEM website.
Whats next? 
Thank you!

You should install it using the normal file upload mode for extensions in Joomla!

In English you find that in the Joomla! administrativ backend in the menu
"Extensions" > "Manage" > "Install" and there the tab "Upload Package File"
(Sorry, I do not know the Greek translations of the Joomla! menus.)

Thank you.
I did that!
Whats next? How I will see the module in front end in Greek language? 
I mean by default the month is shown : December .
I need to say:  "Δεκεμβριοσ"  which is December in Greek.
 

Hi, sorry I don't speak and write in greek language. (I only learned the "old" greek language.
But I tried to install the language in joomla and in JEM.
a lot of words (e.g. from columns and dates) are translated, but e.g. the event description is in english letters and I don't know how to change that in joomla. event descriptions should work like articles in joomla. So there must be some settings.
I hope, you will get some answers and hints from a greek user!