Hello Haitham,
you can do this under
Maps / Wireless Maps / Site Maps
after uploading the floor map than select planning mode under the select a command in right side top..
the link and video link will help you step by step how to do this.
https://www.youtube.com/watch?v=m7XTgt8LahY
http://www.cisco.com/c/en/us/td/docs/net_mgmt/prime/infrastructure/3-1-4/user/guide/pi_ug/wireless-maps.pdf
HTH
good luck