Hi.
Thank you for contacting us and sorry for the late response.
1. If you want to add the custom field to the job package, please go to JobMonster/ Custom Fields/ Job and scroll down to the bottom, you will see the option: "Fields to add to Job Package": https://prnt.sc/CuQE-a-5IPoH
2. After adding the field to the job package, please go to Products/ select the job package product that needs to edit, you will see the fields from step 1 in the Job custom fields: https://prnt.sc/d1de3Od64puw
Select the field for the package you want.
Please recheck it.
Thanks.