I can not set the thermastat so the air conditioner will come on. The vents is blowing but the air is not cool. Help please

First of all here is your manual for the Hunter thermostat you have.

http://www.hunter-thermostats.com/manuals/44110.pdf

Make sure it is wired correctly before anything else.

Now for the questions.

Did you just install the thermostat?

Has the thermostat ever worked on cooling before?

If the thermostat has been installed for a few years and now is just causing a problem then it is probably something else with your system.

Answer the questions and report back.