Exporting cookbooks enables you to send copies of your cookbooks to friends and family who are also using TheRecipeManager.
To export a cookbook, highlight the cookbook you wish to export on the current cookbook list and then 'control-click' or 'right-click' and select 'Export a Copy...' from the context menu.
You will then be presented with the 'Save a copy' window. This allows you to navigate to the location you wish to export the cookbook to. When you have selected the desired location, click on the 'Save' button, and the cookbook will be exported.
You can find out how to import cookbooks at Importing Cookbooks.