To use the Resident Evil 4 HD Project, you must own a copy of the Ultimate HD version of Resident Evil 4 for the PC, which is available via Steam.
Cris and Albert, the fans behind the Resident Evil 4 HD Project which adds new 3D edits, textures, lighting and effects improvements and other adjustments, have released a major update that further improves the PC version of Resident Evil 4.
Here is a video showing how Resident Evil 4 looks after the HD Project mod is applied.
Here is a full list of what the Resident Evil 4 HD Project team has prepared in this third release, as noted on the official website.