Sorry to ask for a stupid question, the answer is probably in the documentation, but I am starting a new project in a new environment for me, so much stuff to learn!!! 
This is an example coming from the Microsoft .Net documentation:
The number of characters in this instance.
How I can easily get the link to System.Int32 in my own doc?
Thanks
I'm not exactly sure what you're asking, but if your product has properties that inherit from the underlying .NET framework, then Document!X handles the links to those .NET properties automatically. You don't have to add anything manually. The links are generated for you.
Hope that helps. Keep going!
Document! X automatically hyperlinks to .NET framework types in the content that it generates (e.g. syntax sections etc.).
If you want to include a link in the content you are creating (e.g. in source comments or a Document! X Content File) you can do so like this:
%T:System.Int32%
That text will be converted to a hyperlink to the .NET framework docs in the generated output.
Richard,
Thanks, this is exactly what I wanted to know 
I've tried this in a topic file for the object type by inserting %T:System.Object% and I get a project link error and it doesn't appear as a link in the built help file. How do I add a link to the VS2010 documentation in a topic file? Also if I want to link to a generic class like List<>, what would the syntax be?
You can create hyperlinks to MSDN pages using the following href: http://msdn.microsoft.com/query/dev10.query?appId=Dev10IDEF1&l=EN-US&k=k(keyword). Where keyword would be the type you are linking to e.g. System.Int32.
You can link to generic items using the ` character followed by the number of generic items e.g. System.Collections.Generic.List`1