how do we copy just one file myfile.txt to a document library programatically

Hi, i narrowed down my needs to copy one single file called for example myPath\myfile.txt which is in my local disk windows folder to the document library called myDocLib of the site mySite of the master site myMastersite in the url: myServerUrl.

P.S I just specified that myPath\myfile.txt  is located in my local drive and not yet in sharepoint.

Thanks for you help.