1) Go to IISManager and find the identifier for your Web Site. Click on the web sites folder in IISManager and on the left side you should get the list of web sites and their identifier

(2) Open a command prompt and runt the following 3 commands. Change the <identifier> with the identifier value found in the previous step
cd c:\inetpub\adminscripts
cscript adsutil.vbs set w3svc/<identifier>/root/NTAuthenticationProviders "NTLM"
iisreset

 

NOTE:

(1) if you want to set NTLM at a virtual direcotry level then use the below command and replace <virtualdirectoryname> with the virutal directory name
cscript adsutil.vbs set w3svc/<identifier>/root/<virtualdirectoryname>/NTAuthenticationProviders "NTLM"

(2) To revert back to Kerberos use "Negotiate,NTLM" as the parameter

(3) To check what is currently set use the below commands
cscript adsutil.vbs get w3svc/<identifier>/root/NTAuthenticationProviders
cscript adsutil.vbs get w3svc/<identifier>/root/<virtualdirectoryname>/NTAuthenticationProviders