Updating wifishield firmware

Hi, I'm trying to update the firmware of the Wifishield with these instructions

When I
Open a Terminal window and move to the path were you saved the script and type as following to get the help:
Mac: ./ArduinoWifiShield_upgrade.sh -h

I receive this message in return:
-bash: ./ArduinoWifiShield_upgrade.sh: Permission denied

Does anyone know how can I solve this?

Many thanks