Long Game promo codes can be redeemed in app. To find the redemption page tap your level on the top left corner of the home page then tap Share & Redeem Codes. On the next screen tap the words "Redeem Code" then enter your code.
Some promo codes are referral codes. You can only be referred by one person. This means that you can only put in one other person's promo code.
Long Game sends out new codes in emails, newsletters, and special promotions from time to time.