My Tibetan mastiffs won’t stop barking (woof)

I got 2 dogs. Both Tibetan mastiffs. They keep barking at stuff. One is 2 one is 6. I just want em to calm down bro like I understand you wanna bark but please

Kindly help. How do I train em to not bark unless it’s actually an intruder or sum which it never is.

Thank you so much for reading😻