2000 blazer wont start

Alright 2000 chevy blazer ls v6. The other day cleaning car out listening to car cd player and blazer died. Jumped it with my other truck and started right up. turned truck off came back later to move into garage and wouldnt start. Tried to jump again and wouldnt start...it made the usual clicking sounds and the accesory lights all were on. Had local auto part shop check battery, needed new one. Installed later and worked GREAT! Next day drove around no prob. Ran like a champ. This morning turn the key and nothing, no lights, no clicking, NO sounds, no nothing. Its like there was a battery switch installed and it was off. The hazards dont even work. I read something about checking fuses but i am not sure which to check..and thats about all i know! Any assistance would be sweet!!

1.) Did you charge the battery before you installed it?

2.) Check the battery voltage now with a voltmeter.

3.) Alternator is probably shot.