To change or edit property of the field:
Navigate and hover to the field in Doctype editor, you will see the "Edit" icon on the right side of the field. click on "Edit" icon beside field which you wish to edit.
Field Editor window will appear in pop-up, make necessary changes, Click on "Done" button and save the Doctype.
In field editor, there are field properties by using which you can customize your fields.
Label: Field label is display title of the field, You need to set your Label according data you want to collect from the user.
Is Required: Check this option to make your field as mandatory, user can not save the form without filling this field. such type of fields are generally used for essential data to be captured for example: Serial Number, Name, Phone, Email etc.
Is Read-Only: Check this option to make your field as mandatory, user can not edit or update this field, such type of fields are generally used for reference or calculation purposes, for example: Status, Grand Total, Amount, Updated On (Date) etc.
Is Hidden: You can make your field as hidden or invisible to user by selecting this check box, user can not view this field in form view of the Doctype, but you can fetch the data of this field in Custom Scripts, and Reports.
In List View: You can make your field visible in List View of the Doctype, User can view the data of such fields in list view without opening form view of each Doctype.
Must be unique: By selecting this option you can capture non-duplicated or unique data, user cannot create record if data entered in such field is similar to data entered in same field in another record of the doctype, such type of fields are generally used for capturing unique data to avoid duplication, for example: Company Name, Customer ID, Mobile No, SSN, E-mail ID etc.
Description: You can add field description to add help text or field information which help your user to understand what data they shall to provide.