Just select the recipes, right click and select "export selected" to export them to a BSMX file. On the Mac side, open the BSMX file using File->Open, then select the recipes you want to keep and copy/paste them into My Recipes to store them.
Alternately you can also transfer them by just copy/pasting into your cloud folder if you upgrade the windows side to 2.2 (its a free upgrade). Videos on the cloud here: http://beersmith.com/video
Brad