Store all downloaded parts in the same folder.
Ensure you have enough storage space. You need room for both the compressed RAR files and the final, extracted file.
Based on your request, it seems you are trying to download or handle a large file that has been split into smaller parts (a ".rar" archive).
Here is the essential information for dealing with multipart RAR files:
Right-click the first file (.part1.rar or the file without a number) and select "Extract Here" using a program like WinRAR. The software will automatically combine all the parts into one file.
If you are seeing an error, it is likely because one of the split files is missing or corrupt.