Hi Paola,
if you own IMAQ Vision you can just have a look at the examples that comes with your board or you can look at: http://zone.ni.com/devzone/explprog.nsf/6c163603265406328625682a006ed37d/2abaefe05789961686256866007c0d22?OpenDocument.
Without IMAQ Vision look at:
http://zone.ni.com/devzone/explprog.nsf/6c163603265406328625682a006ed37d/22474456534202b086256aff005fc4f3
(or search at ni.com for "IMAQ Display without IMAQ Vison)
Please mail me if you need further help,
Michael