Right-click Part 1 and select "Extract Here" using WinRAR or 7-Zip; the software will automatically pull data from Part 3.

Are you getting a (like a checksum error)?

Ensure you have at least 10GB of free space on your drive for the full extraction of all parts.

Ensure you have downloaded all parts (Part 1, Part 2, etc.) into the same folder before extracting.