FOLLOW BELOW STEPS.
1. Login with the FF ID with Google, Facebook or with any other app.
2.Then enter the Redeem code .
3.Make sure that the redeem code is valid.
4. Once it accepts your redeem code then your reward will get in your message (Mail) section in your FF ID.
SOME IMPORTANT POINTS YOU SHOULD TAKE CARE OF:-
1.Redemption has 12 characters so check before you enter.
2.Reward will add to your mail box and Money and Diamond will directly added to your account.
3.Check weather the redeem code is not expired. Most of the site redeem code are expired.
4.And if you tackled all of above issues and having problem then you may contact to customer care on Reward.ff.garena.com
5. And the most important thing you can redeem reward if you play in guest ID.
You can Link your Guest ID with your Google or Facebook in order to get your rewards.