You can create links within your posts, and each post has a unique URL (known as the "permalink"), so you can add a link from one post to another just like you would add a link to any other page. Is that what you are asking?

It is. I have done some external http links, but can't see how to do internal ones.

You can do them the same way as external links. Just put in the full URL to the post (domain name and all). That will only become a problem if you move your blog from one domain to another (but even then, you could easily fix it with a find/replace MySQL script).

Ummmm. If that's the only way I don't think I'll bother. I wouldn't even know how to find the document!
Thanks anyway I'll just leave it.