Mostafa,
in the simplest situation, in Query editor you only need to set the criteria equal to
Now()
However, you will find that because of the way access stores dates there's a hidden time included with the date (00h00)
So often one may have to use something like:
>= [Now()] < [Now()] + 1
And there's a twist on the date is stored so that if the date is stored: mm/dd/yyyy hh:mm:ss and you only enter m/d/yy then search may fail.
Please refer to:
Dealing with international dates:
http://allenbrowne.com/ser-36.html
Please check you PM in a little bit, I'll forward you my boilerplate of general links and tutorials that should help you get things going.