Mothership Zeta is an add-on for FO3. Since you've asked this question in the PS3 section
, i'll have to assume you are playing the game on that console.

Add-ons are not currently available for PS3 , but they will be shortly via the Playstation
Store. And on october 13th a 2 cd FO3 game will be released with all the add-ons included.


Once the add-on is either downloaded or the 2nd CD inserted. You will receive an
unintelligible radio transmission , leading you to the alien crash site. Once you have
found the crash site you will be "beamed" up in the mothership.

you can't buy the addon packs yet, or buy game of the year edition

the GOTY edition came out on ps3 october 13th , i should know i bought it.