Open part01.rar using a utility like WinRAR or 7-Zip. These tools automatically detect and extract the data from subsequent parts like part03.rar .
Downloaded aircraft add-ons should be unzipped and moved into the X-Plane 11/Aircraft folder. X.Plane.11.v11.32.R2.part03.rar
If you are looking to expand your installation once updated: Open part01