the 95MB+ package from the Microsoft Download Center.
If you are using the June 2010 redistributable for an offline installation, follow these steps: directx 12 windows 10 64 bit offline installer link
To check if DirectX 12 is already active on your 64-bit system: How To Download & Install DirectX 12 (Windows 10 & 11) the 95MB+ package from the Microsoft Download Center