If you need to add either a new user, or update an existing one the command is rather simple:
GRANT ALL PRIVILEGES ON *.* TO 'user'@'8.8.8.%' IDENTIFIED BY 'password' WITH GRANT OPTION; FLUSH PRIVILEGES;
This would add anything in the 8.8.8.* netblock, with the user named “user” and the password “password”
You could wildcard to make it any ip with just a %, or you could specify an exact ip. YOU MUST specify password every time, even if you are only adding an ip.