Hi again Aydin:
To use the Special artillery you need a convination of elements.
- Unlock Fire Direction Center
- Build an infantry observation unit and move it to the artillery foxhole and activate the binos.
After that:
a. Go to your main base and click the Fire Direction Center. In there you will have the off map artillery. The only ability ready to use is the pack howitzer off map, the other two needs to be unlocked by tech tree.
b. Other option is to check your base building menu. We add an option in the fast selection bar down and right in your screen. Remember again you need to “unlock by tech tree” the Fire Direction Center to get access to that.
I hope this could help