Passing an authentication(username/password) to the sharepoint site (avoid prompting window authentication)

Hi,
We have a link in our site that pin points to sharepoint documents and we are retreiving some documents files (*.doc). Our sharepoint uses IWA (integrated windows authentication) which is prompted if we're trying to access that documents, unfortunately we don't want to prompt that window to authenticate the user. We need is to create a username and password and authenticate it. how can we do that.
Note* we have 2 server one for our application and the other one is for sharepoint.

thanks in advance.

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