Hi @berne welcome on board!
You are editing a Javascript file. You can basically use any decent text editor to edit this file, however some will mallform the file. Thats why I recogmend you something like Notepad++, or Visual Studio Code.
You just have to add this somewhere in the modules array (An array is a list of things)
For example:
modules: [
{
module: "alert",
},
{
module: "MMM-NowPlayingOnSpotify",
position: "top_right",
config: {
showCoverArt: false,
clientID: "",
clientSecret: "",
accessToken: "",
refreshToken: ""
}
},
{
module: "updatenotification",
position: "top_bar"
}
]
Note, there must be a , character after the last } if this isn’t the last module. You can easily validate your changes by using a Javascript Linter.