In order to upload file using selenium we need to locate the upload button 
in the DOM html. Then we do sendKeys by passing the path to the file. 

First, I locate the element which takes the path of the file(Choose file button) :
      WebElement input = driver.findElement(“id”); 
 And then I provide the path to the file using the sendKeys method :
      input.sendKeys(“/path/to/file” + Keys.ENTER);