Go to the transformations menu and select the rotate option. Set the configuration for rotation around the bottom, 60 degree angle, and 5 copies. This will give you all six arms of the snowflake. If you don't like the final shape, go back a step and modify the design of the single arm, then repeat this step. Once you are happy with the final appearance, select the weld option again to merge all of the arms into a monolithic snowflake.