ZMAF is the armed forces of Zemlya Mechty a country of the coast near Russia, the regular forces were trained by the Russian army ans the special forces were trained by the infamous Russian Spetnaz Operatives. The regular army carry AK'S while the Special forces carry the more modern AK-12 while carrying some dated combat helmets and vests.
To install ZM Armed Forces you should use modfolders to keep it seperate from the official game content to prevent issues.
With Arma 3 you can use different ways to set up your modfolders to use custom content you have downloaded.
Please visit the Arma 3 Mod install instructions page
for more information about using custom mods and addons in Arma 3.