Modules in Airflow

Question

I have several classes defined in Python which represent jobs. In my orchestrator I define the needed functions for Airflow as follows:

from jobs.package.job import ToBeExecuted

def run_job(**context):
    ti = context['ti']
    date = context['ds']

    job = ToBeExecuted()
    input = ti.xcom_pull(task_ids='previous_job')
    output = output.csv
    job.run(input, output, date)

    return output

As mentioned in the Airflow docs (https://pythonhosted.org/airflow/concepts.html?highlight=zip#packaged-dags), you cannot use external packages without packaging them.

But I just don't understand the described solution. You package everything in the zip folder, but then what? How do you launch it? How do you backfill it?