Hi @sujitnath84,
you can always add a workflow description (by clicking a blank spot in the workflow canvas, then hit the pen in the upper right corner of the description view) which will be shown in the WebPortal:
KNIME AP: 
WebPortal (in the List):
WebPortal (when clicked):
If you want to add descriptive text in the WebPortal, e.g. on each page of your DataApp, I’d recommend the Text Output Widget, where you can add plain or HTML-formatted text.
If you meant the documentation of the workflow itself, I’d recommend e.g. workflow annotations (again, right click at a blank spot → New Workflow Annotation).
Best,
Lukas