Modern versions of Windows include full Direct3D 11.1 support, along with Direct3D 11.2, 11.3, and 12. Windows Update will automatically keep your system components up to date.
If your GPU is an older model (e.g., NVIDIA GeForce GTX 560 or AMD Radeon HD 6870), you are at a dead end. You cannot "download" a hardware upgrade. d3d feature level 11.1 download
A feature level always includes the functionality of previous, lower feature levels, meaning that a card supporting 11.1 will also support 11.0, 10.1, and so on [9†L19-L20]. Modern versions of Windows include full Direct3D 11