(Attock VU Group)

i have problem in nasm when  i run my programme on command prompt then this statement show on command prompt "nasm is not recognised as external or internal command,operable program or batch file" plz tel m what i do?

--
█████████████████████████████████████████████████
██████████████████ Basic Group Rules ███████████████████
Immoral & Rudish talk, Earning program links, Cell number for friendship purpose, Websites/Groups Links, Adult contents, Criticize-able Islamic stuff, Spreading disruption, Spamming are strictly prohibited and banned in group.
█████████████████████████████████████████████████
█████████████████████████████████████████████████
 
Follow these detailed Group Rules, otherwise you will be banned at any time.
https://docs.google.com/document/d/1YJxA8x3_U7C1lRc0EXfLrJpco4A1XkB1vDxOTqOd3Jg/edit?hl=en&authkey=CNDy9tkJ
 
Group Email Address:
Attock-VU-Group@Googlegroups.Com
 
Join group by sending a blank email from University ID at:
Attock-VU-Group+Subscribe@Googlegroups.Com
 
████████████ Click here to Join this group at Facebook:████████████
♥ ♥ ♥ https://www.facebook.com/home.php?sk=group_111877855568034 ♥ ♥ ♥
█████████████████████████████████████████████████