To switch to the second weekend replace the 1 with a 2.
Found on Reddit. Need a citi card to access but after that you can pay with a different card.
Citi Private Pass GA Package - Weekend 1
Experience the Coachella Valley Music and Arts Festival with performances by Outkast, Muse, Arcade Fire, Pharrell Williams, Lorde, Skrillex, and more. Citi card members receive access to purchase GA packages to the sold-out festival.
GA Packages - $585 per weekend and includes access for one (1) person to the following:
(1) 3-Day GA Festival Pass
(1) Shuttle Pass
(1) Hard Rock Coachella Weekend Ticket