I would point you to this:

https://github.com/franton/CIS-Apple-Security-Casper/tree/master/2.6.3%20Enable%20Firewall

That's an EA to detect firewall setting and a script to turn it on.

Oh and if you want firewall stealth mode on too, then I have this:

https://github.com/franton/CIS-Apple-Security-Casper/tree/master/2.6.4%20Enable%20Firewall%20Stealth%20Mode

thank you i going to use the stealth mode

You will have to use both The first detects whether the firewall is on or not. The second sets stealth mode on/off. So the firewall must be on for the stealth mode setting to have an effect.

Can these scripts be pushed out using Jamf Now?

Even I want to know how do we push these scripts 

You can create a configuration profiles so,

1. Create a configuration profiles, under Security and Privacy you can enable Firewall and add the firewall exclusion that you want

2. Define the scope of the computer where you want to apply this profile. 

3. The firewall of user OSX will be controlled by Jamf now (when the Jamf policy sync in). 

works like a charm