Please READ the user manual, or at least, the installation guide that should come with it.
Make sure that all components have fresh batteries and are turned ON.
Make sure that the receiver is correctly connected to the correct USB port. On most laptops, it's the one on the right side. Mouses and keyboard tend to refuse to work if connected to ports on the left side.
If after checking all of your USB ports it still don't work, try with another computer.
If it still don't work, return it to the place where you bough it to get a refund or replacement.