I have set my blog so that people has to register and get login name/password to post a comment. How do people request to register as a user? Do they have to call or email? Can they request it on the site (do I provide a page to do it)? Sorry it seems such an elemental question, but so far I can't find the answer although I looked for the answer in WordPress and this forum and help pages... Thanks.

In the WordPress Dashboard->Settings->Discussion->Other comment settings

I had check-marked "Other Comments" setting on "Comment author must fill out name and e-mail" and
"Users must be registered and logged in to comment". This is why my question arose. I still don't understand how people register to be able to log in. When I tried to write a comment as a non-admin (for testing purpose), the login/password entry page appeared, but didn't give me a page to register first. Sorry I'm such a deadhead.

I donated last month. I could donate to you this month. Or is it the same thing? All your helps are much appreciated.

Sorry, between Atahualpa and Wordpress, there are a lot of options.

If you go to the dashboard->settings->General->Membership is a check mark to allow anyone can register. If you have the 'Meta' widget in the sidebar, you will now see a new entry 'Register'

There are also some 'Register' widgets, do a google search with 'wordpress register widget'