I've logged in to my account using Stack Exchange OpenID. That is, I just clicked the "log in" link in the top bar, and typed in my e-mail address and password.
If you're on a shared computer, remember to log out of your Open ID provider (Facebook, Google, Stack Exchange, etc.) as well.
Alas, the page completely fails to explain how to do that. Facebook and Google, of course, have their own logout links in their own user interface, but the Stack Exchange OpenID provider, and its logout page, is completely hidden from normal users.
Of course, I've been around for a while, and I've spent some time hacking the SE interface, so I happened to know that I could type
openid.stackexchange.com into the browser's URL bar, and follow the "logout" link to this page. But that's totally a hidden feature, and I don't think there's any way for an average user to figure it out without trawling through old meta posts.
Please add some way to get from the logout page to https://openid.stackexchange.com/, e.g. by making the underlined text in the screenshot above a link. Or provide some other way for people using Stack Exchange OpenID to log out properly, e.g. by making the logout form also log you out from the SE OpenID provider, if you're using it.
(See also: A related general feature request that I made two years ago, that led to the current footnote being added to the logout page — but, alas, without the link. Note that the logout interface has otherwise changed substantially since that request was made, so some parts of it may no longer be relevant. In any case, this request is a more specific one, and hence IMO worth making separately.)