add text to the banner slider.

How do I add text to the banner. I would like text come same as in the demo. A heading in bold and some normal text following.

Well I guess you're talking about Responsivebannerslider module here.
If that so then to have that heading and text below it, you can manage them for your Banner Management

components->Banners->Banners

for each banner item you have, please fill in this field

Alternative Text -> for the heading
Description -> for text below the heading.

Also you might want to read the module documentaion inside the module package.