Once you've created a model, be sure to select the "Publish" option when saving it online. The publish option is described at: www.bikecad.ca/permissions. I would not include your design in the public Design Archive, unless you are looking to get feedback from other people in addition to your builder.

By publishing your design, you will have created a web page with an image of your bike and a link to download the BCAD file. Simply e-mail your builder the URL for this web page and the builder should be able to use BikeCAD Pro to get all the information needed to build the frame.