read only filesystem error

when i try to change permission chmod -R 777 /Volumes/Sublime_Text_3/Sublime Text.app

i get error saying Read-only file system, how can i change it read write access to /Volumes/Sublime_Text_3 and everything inside it

i have tried with sudo as well but i get same error message

Is that volume an external disk or a network share?

ok, got it when i was installing Sublime it made mount to disc, which was why i was getting read only message...