Sorry this is such an obvious question.
I've installed WP with multisite - for directories not domains.
The 'Tools -> Network' option appeared and I followed the instructions, after which the 'Tools -> Network' option disappeared. 'My sites' appears and lists my top level site.
I've checked every menu option and I cannot find anyway to create another blog. I've read lots of postings regarding the 'Super Admin' menu, but I understand this is no longer used in 3.2.1 - It certainly doesn't appear as an option in my menu, so how do you create another blog?
Reading the forums I've seen lots of posts with similar problems. So far I've re-installed WP to start with a fresh install. Double & triple checked the .htaccess and wp-config files and both seem to be in order (wp-config defines above the '/* That's all, stop editing! Happy blogging. */' line). The Multisite tables have been created in the database. I have only 1 user - Admin (fresh install), and the quotes in the files are not smart quotes.