When i choose field change template

Hi, please try this:

1. Navigate to Settings > Service Desk Templates > Sub Types.
2. Select the sub type you wish to add a description to or create a new one if necessary.
3. Within the sub type configuration, locate the description field and ensure it is added to the visible fields list.
4. If the description field is not present, you may need to add it from the available fields.
5. Enter the desired description in the appropriate field.
6. Save your changes to the sub type.