Step 1: You will have to download this software only in your mobile so be sure you have Internet Package activated to your mobile number.
Step 2: Open your mobile browser and in the address bar type "en.softonic.com" .
Step 3: In the search box type "whatsapp" and operating system select "Java2ME" this will be default in your mobile browser. (Only .jad files will be supported by Nokia Asha 205)
Step 4: Download and install.