XWPFDocument doc = new XWPFDocument();

FileInputStream fis = new FileInputStream("/images/image.png"); 
XWPFParagraph par1 = doc.createParagraph();
XWPFRun runAppName = par1.createRun();  
runAppName.addPicture(fis, Document.PICTURE_TYPE_PNG, "image.png", 257, 185);

doc.write(new FileOutputStream(new File("/folder/document.docx")));