If what you are referring to is the content of a custom channel field tag, then you can edit the content of that within the channel entry: Content -> Edit
If it's a global variable you are referring to, then you can edit the content of that under Design -> Templates -> Global Variables. It could be a snippet, another type of variable, and for that you can edit the content at Design -> Templates -> Snippets.
It should be in one of those three places. Channel Tags, Global Variables and Snippets all have the {} brackets, so look the same on templates, although channel fields only would be inside of a Channel Tag pair.