Modifying XML values using C#

Hello everyone,

I'm trying to create a program where I can 'log' certain values. For example, I want to know how many cookies I eat each day. The 'total' should read the total amount of cookies I ate and the 'add' should add up x to the total cookies I ate already.

<food>
	<cookies>0</cookies>
</food>

What is the best way to start this? I'm quite a novice when it comes to C# programming, but I felt like this was a good way to learn how to interact with XML files.

Any help is appreciated. Thank you very much in advance.