First make sure you have GeoDjango correctly setup and a PointField field defined in your model, then add a GeoPanel among your content_panels.
from django.contrib.gis.db import models
from wagtailleafletwidget.edit_handlers import GeoPanel
class MyPage(Page):
location = models.PointField(srid=4326, null=True, blank=True)
content_panels = Page.content_panels + [
GeoPanel('location'),
]