Where to place blocks of code

I am attempting to implement the code as displayed in the example. For example, when I place this in the app delegate:

import SQLite

let db = Database("path/to/db.sqlite3")

let users = db["users"]
let id = Expression<Int64>("id")
let name = Expression<String?>("name")
let email = Expression<String>("email")`

It seems to work okay. But then when I go to use the create table code:

db.create(table: users) { t in
    t.column(id, primaryKey: true)
    t.column(name)
    t.column(email, unique: true)
}

It doesn't seem to like it. My understanding is the table creation code needs to go in a method. But which method does it belong in? Or in a new method altogether?

Sorry if the question seems simplistic. I'm new to Swift as well as to SQLite. :-)