You can delete or remove a field by navigating to the Layout tab and clicking on the settings cog on the right of it and clicking the “Remove Field” or “Delete Field” button.
Removing a field will simply remove it from the column that it is in. If you want to add that same field back in later, it will be available from the drop-down list when adding a field.
Deleting a field will permanently remove it. If you delete a field, you won't be able to add it back in later – you will need to create a new one.
Default fields that come with the layout cannot be deleted.