First, import the GPG key.
sudo wget -O- https://developer.download.nvidia.com/compute/cuda/repos/debian11/x86_64/7fa2af80.pub | gpg --dearmor | sudo tee /usr/share/keyrings/nvidia-drivers-linuxcapable.com.gpg
Second, import the repository for your Debian 11 system.,
echo 'deb [signed-by=/usr/share/keyrings/nvidia-drivers-linuxcapable.com.gpg] https://developer.download.nvidia.com/compute/cuda/repos/debian11/x86_64/ /' | sudo tee /etc/apt/sources.list.d/nvidia-drivers.list