You must be using the Chrome desktop web browser to export to Draftkings. When you attempt to export, you will be prompted to install the plugin if you do not already have it installed. You can install it directly from here: Fantasy Cruncher Export Tools
You need to be logged into Draftkings on a separate tab in order to export.
After producing lineups, you will see the "show export tools" link at the top of the lineups, clicking this will reveal the export options.
Use the dropdown to select which slate you want the exported lineups to be created under on Draftkings. These are the same slates you will find on Draftkings, and the games you have used to create the lineups need to be available in the selected slate. For example, if you choose an early slate, you can not have late games in the created lineups or the export will fail.
You can individually check or uncheck lineups using the circle checkmark on the lineup cards. You can also select or unselect all with the buttons in the export toolbar.
When you have the lineups chosen that you wish to export, click the "Export X Lineups to draftkings" button. Each successfully exported lineup will be marked with a green check mark and you can go to your Draftkings lineup page to view them.