Apple Script: 'activate' an application in fullscreen
Allow the Script Editor to access Accessibility in System Preferences, &amp; try this script. You should define the application name properly. 

set MyApps to {"Google Chrome", "Skype", "Finder"}

repeat with MyApp in MyApps

tell application MyApp

    activate

    delay 3

    tell application "System Events" to tell process MyApp

        set value of attribute "AXFullScreen" of window 1 to true

    end tell

end tell

end repeat


or if you have a single application then 

tell application "Safari"

activate

delay 3

tell application "System Events" to tell process "Safari"

    set value of attribute "AXFullScreen" of window 1 to true

  end tell

end tell