Ah I see. I already had a Sony Rewards account so I was trying to find it within the account. I didn't check back to see the special link to redeem it after I clicked the OP's instructions. I'm surprised GDD doesn't specify.
I'd like to say thanks for supporting fellow Marines and any other service members out there. This type of thing is a real morale booster, and a lot of times we feel forgotten. Thanks again to everyone who supports this.