If you aren't using virtual channels...
Using the original Acquire&Proc example program, you can set the gain by putting values into the Input Limits. Labview will automatically scale the results. So if your signal is 0-10V, put 0 as the minimum limit, and 10 as the maximum limit. Typically, you''ll use the range of whatever signal you're measuring, but if a higher gain is needed, use a smaller range (liek 0-1V).
See also:
http://sine.ni.com/apps/we/niepd_web_display.DISPLAY_EPD4?p_guid=B45EACE3E8A156A4E034080020E74861&p_node=DZ52300&p_submitted=N&p_rank=&p_answer=&p_source=External
2006 Ultimate LabVIEW G-eek.