can someone tell me how to use ‘sig file’ or ‘signature file’.?

Answer 1

If you are using Outlook there is an option under Tools (or a Tool under Options) that you can use to include a Sig file to all of your emails.

Answer 2

Are you referring to a message board like http://www.iwdn.net?

If so, go to the User CP link and in there should be a link to your signature. You will need to check with the forum TOS though. Some forums don't allow certain things in signatures or not even a signature until you have so many posts