There are various ways to achieve the same.
If you want to keep reading sequentially, you can use XmlReader.
If you want to read/update/delete/insert at particular location, you can use two approaches
1. XmlDocument and XPath.
2. LinQ to XML
For XmlDocument approach, First you declare variable and load xml.
XmlDocument xDoc = new XmlDocument();
Then, you read like
string nodeValue = xDoc .DocumentElement.SelectSingleNode("NodeName").InnerText;
You can update value like
xDoc.DocumentElement.SelectSingleNode("NodeName").InnerText = newValue;
Note, that in above code, "NodeName is actually Xpath. You can give it like Node/ChildNode/GrandChildNode and so on. You can find more details about xPath at http://www.w3schools.com/xpath/default.asp
Hope that helps. If it does mark it as answer/upvote.