Not sure what you are asking for. You can make any field editable. You do that in the Inspector when you are in Layout Mode
Any field of type number, text, date, time, timestamp, or container is by default editable. You have to do something to the field object after adding it to the layout before it is not editable.
Do you perhaps have a field on the layout that is not editable and you think that it should be?
Fields of type calculation are not and cannot be editable.
Fields "grouped" into a button are no longer editable.
Fields that have "browse" cleared in the inspector's data section are not editable.
Fields that have a transparent object--such as a button placed on top of them may not appear to be editable as you can't click into them.
Usually people ask the opposite, how to make uneditable a field that is editable.
How is your field defined ?