How to use Chat for pre-sales query?

Hello there. I want to use the chat for, to quote given in the description of the plugin "Answer pre-sales or support questions".

1. I want a button on the bottom corner of my site where visitors can initiate chat with one of our staff.

2. The site visitors should be able to choose the staff they want to converse with.

3. The online status displayed on staff's buddyPress profile, clicking on which, a visitor should be able to initiate a chat.

Any help??