NO_PUBKEY error when trying to run "sudo apt update"

I was trying to install Sublime Text from the terminal. I followed these steps. I didn't use the update command because I already ran it a day earlier, and started with the second step. Then I started having errors, so this time I also ran the sudo apt-get update command, but now it's showing me this error message.

the error


You did not properly add the GPG key of the repository you have added. Go to step 3 of the link you provided, and try again:

curl -fsSL https://download.sublimetext.com/sublimehq-pub.gpg | sudo apt-key add -