Just downlodaed it yesterday.

How do you get it to start up? The post here says start any gam except ones that involve the ending. I am not sure what that means.

My character just gained level 30 and about to attend the speech at Hoover Dam. Is that too late?

I don't see any new locations on my map and no notices have appeared on the PIPBOY either.

Are you at the final quest or at President Kimball's speech?
Cause if you're at Hoover Dam for the final quest then you have to reload a save outside of Hoover Dam or create a new character.
But if you're at President Kimball's speech then I dunno, maybe just walk around for a while until the messege pops up or remove the DLC and re-download it.
Hmm, do you have the latest patch?

At the speech so I don't think that is too far.

How do I know if I have the latest patch or not?

I will play around some more this evening and see if it works. WIll get back to you. Thanks.

Well I dunno if the patch has been released on the PC or PS3 yet so I dunno if you're playing on something other than the 360 but I think that for all three systems as long as you are connected to the internet they will all automatically download the latest patch for you.