Create multiple kml files in Python
In your first code you already have everything you need, you just don't use it. List2 and List3 are each lists of points to create. But they only contain one point, so your for loop does nothing exciting, it only runs once.

You can simply add more points to any of the lists, here I take the first as an example:

import simplekml

points = [['Placemark', 'old file', 51.500152, -0.126236],
          ['New placemark', 'new file', 51.600152, -0.136236]] # description, lat, lon

kml = simplekml.Kml()
for point in points:
    kml.newpoint(name=point[0], description=point[1],
                 coords=[(point[3], point[2])])  # lon, lat, optional height

kml.save("test2.kml")


You could make this a bit more readable by using a collections.namedtuple for the markers. This way your comments become superfluous:

from collections import namedtuple
import simplekml

Marker = namedtuple("Marker", ["name", "description", "lat", "lon"])

points = [Marker('Placemark', 'old file', 51.500152, -0.126236),
          Marker('New placemark', 'new file', 51.600152, -0.136236)]

kml = simplekml.Kml()
for point in points:
    kml.newpoint(name=point.name, description=point.description,
                 coords=[(point.lon, point.lat)])

kml.save("test2.kml")


Note that I followed Python's official style-guide, PEP8, when naming my variables. Variables and functions should be lower_case and only classes (such as the namedtuple class I create) should be in PascalCase. PEP8 also recommends putting a space after commas and not to use unnecessary whitespace.