How do I do this please?

There are plenty of things you could use to store something.

* Database (Remote)
* Serialize (Binary File, local)
* Serialize (Text File, local)


For storing something in a database you need to know sql, you need to own a database server.
There are plenty of serverprograms out there, some are: mysql, postgresql, oraclesql,...

For Serializing I can only give you some links:
Yaxlib. Xml Format, human Readable
General MS Documentation
Xml Serializer from Microsoft

Or you can write a serializer on your own.
This is a example which writes a String[] to a file and reads it again. Note you can't use '~' in the string.

string[] tok = {"test", "test", "test", "test"};
...
String toFile = "";
foreach (String s in tok) {
    toFile += s + "~";
}

File.WriteAllText("myfile.txt", toFile);

and for reading this could be your solution:

String text = File.ReadAllText("myfile.txt");
String[] arr = text.Split('~');