How can i add a new field to my table (collection)?

i have this picture, that is a table, i want to add a new field to my table

the structures is following as:

cities: colleges:fields:attributes

i want to put a new field, i was trying

const myNewField ={
 name: chair
 notebook: true
}
db.collection("cities").doc(city.id).update(myNewField).then(function() {
        console.log("Document successfully written!");
       });

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