XML : How can I create a new xml node in an existing xml document?

I have xml file where I save my settings for my application

  <?xml version="1.0" encoding="utf-8"?>  <Settings>    <Version>Growthanalyzer v1.0.1</Version>    <Update>Automatic</Update>    <Databases>      <Database>        <Name>RoomOne</Name>        <StartMeasureTime>10/5/2015 12:00:00 AM</StartMeasureTime>        <EndMeasureTime>11/12/2015 12:00:00 AM</EndMeasureTime>        <FirstMeasureTime>10/27/2015 12:00:00 AM</FirstMeasureTime>        <LastMeasureTime>11/24/2015 12:12:13 PM</LastMeasureTime>          </Database>    </Databases>    <Archives>      <Archive>        <Name>RoomOne</Name>        <FirstMeasureTime>10/27/2015 12:00:00 AM</FirstMeasureTime>        <LastMeasureTime>11/24/2015 12:12:13 PM</LastMeasureTime>      </Archive>    </Archives>  </Settings>    

To start with I will have have one database and one archive, but in the future it is possible to have more databases and archives. I would like to save information for these things in an XML file. How can add another Database node and Archive node like this template, dynamically when user clicks some button.