Hello @GloomyLake935,
All you need to do is redeem the rewards as a MS gift card. It will then be applied to your account, and it will use that first before any “real” monies. 
Hello @GloomyLake935,
All you need to do is redeem the rewards as a MS gift card. It will then be applied to your account, and it will use that first before any “real” monies.