Hello sunny dee,
You can open up the DAQ Assistant and just click on the button that looks like a piece of paper (next to the red "X") above the channel list. This will allow you to add other channels to the current task. Make sure you have the DAQ 7.4 driver, otherwise I believe that it will only let you add channels of the same type. The link to the DAQ 7.4 driver can be found here:
http://digital.ni.com/softlib.nsf/websearch/90B60D5899BCCCDB86256FC700581B89?opendocument&node=132050_US
Take care,
E.Lee
Eric
DE For Life!