When you have qualified your lead into an opportunity, you send them a quotation. 

To send a quotation clicking on any opportunity or lead, you will see a New Quotation button, it will bring you into a new menu where you can manage your quote.

You will find all your quotes to that specific opportunity under the Quotations menu on that page.

Mark your opportunity as won or lost to move the process along. If you mark them as won, they will move to your Won column in your Kanban view. If you, however, mark them as Lost they will be archived.