How do I use spaces in the Command Prompt?

Single quotation marks won't do in that case. You have to add quotation marks around each path and also enclose the whole command in quotation marks:

cmd /C ""C:\Program Files (x86)\WinRar\Rar.exe" a "D:\Hello 2\File.rar" "D:\Hello 2\*.*""

I just figured out that for a case where the path involves the use of white space characters, for example, when I need to access the app xyz which location is :

C:\Program Files\ab cd\xyz.exe

To run this from windows cmd prompt, you need to use

C:\"Program Files"\"ab cd"\xyz.exe

or

"C:\Program Files\ab cd\xyz.exe"

If double quotes do not solve the issue then try e.g.

dir /X ~1 c:\

to get a list of alternative file or directory names. Example output:

11/09/2014 12:54 AM             8,065  DEFAUL~1.XML Default Desktop Policy.xml06/12/2014  03:49 PM    <DIR>          PROGRA~1     Program Files 10/12/2014  12:46 AM    <DIR>          PROGRA~2     Program Files (x86)

Now use the short 8 character file or folder name in the 5th column, e.g. PROGRA~1 or DEFAUL~1.XML, in your commands. For instance:

set JAVA_HOME=c:\PROGRA~1\Java\jdk1.6.0_45