How do I get the “Jar of Souls” and "Matriarch's Bones" achievements?

I cleared the beta (killed the Skeleton King) twice with my Demon Hunter, and didn't get either of these achievements.

I've searched in the open map and cathedral. Is it in a crypt?

Where can I go to get these events?

The Jar of Souls is in one of the two false (one-level) Defiled Crypts in the cemetery. At least one will have the "Jar of Souls" or "Matriarch's Bones" Event quest (though it's impossible to predict which). A handy trick: leave the game if you have the wrong one, as the event could reset to the Jar instead.

You'll enter a room with a blue jar and enemies will attack you for a minute. Then it'll pop.

Diablo is known for its random quest generation. There is no guarantee that you will have the opportunity to obtain the quest on a given playthrough.

With that said, if it appears, it is in one of the incorrect Defiled Crypts in the Cemetery of the Forsaken.