Answer:
As you read this letter, please consider the fact that my Nintendo 3DS is still under full warranty.
Include original pertinent documents
Step-by-step explanation:
When asking for a warranty to be effective you just have to communicate your problems and let the poeple know that you want to use the warranty and have a new device, in this case you would let them know in a calm and simple way that you wich to have your nintendo repaired or replaced because it is under full warranty, and you need to attach the proper original documents to prove that.