Here is the link to register for postseason Cubs codes:
https://securea.mlb.com/chc/ticketing/postseason-ticket-opportunity/
2016 Cubs Postseason Ticket Purchase Opportunity Timeline
NLWCG, NLDS, NLCS and WS REGISTRATION PERIOD BEGINS: 9 a.m. CDT, Wednesday, September 7, 2016
NLWCG and NLDS REGISTRATION PERIOD ENDS: Noon CDT, Wednesday, September 21, 2016
NLWCG and NLDS SALE FOR DRAWING WINNERS: Details will be communicated via email directly to the winners
NLCS REGISTRATION PERIOD ENDS: Noon CDT, Friday, October 7, 2016
NLCS SALE FOR DRAWING WINNERS: Details will be communicated via email directly to the winners
WS REGISTRATION PERIOD ENDS: Noon CDT , Monday, October 17, 2016
WS SALE FOR DRAWING WINNERS: Details will be communicated via email directly to the winners