Bill Clinton’s page (along with other pages that are vandalized frequently) is protected. That means you have to have a Wikipedia login to edit it (and it may be that you have to have had the account for a while). Once you do, there’s an “edit this page” tab on top of the article and “edit” alongside each section.
Most of the pages of notable people are pretty closely watched though, and vandalism there usually gets reverted pretty quickly.
Not really, but as you’ll see now, it’s already been fixed. Wikipedia is notorious for both vandalism, and for quick fixes. Bots sweep through and revert much of the vandalism; that which isn’t caught by a bot is fixed by one of the thousands of people online browsing at any given time.
Actually, it wouldn’t be a formal report or anything, but you could post about it on the article’s talk page (I don’t think those are usually protected). That’s the link at the top that says “Discuss this page”.
You could, but it wouldn’t really be anymore beneficial than waiting for someone to fix it. For example, this particular vandalism bit has a history of:
14:41, 5 March 2008 Orangemarlin (Reverted 1 edit by Dames games identified as vandalism to last revision by Mangwanani.using TW)
14:40, 5 March 2008 Dames games (→Early life)
With no reporting, this bit of vandalism (on a Wednesday evening close to midnight) was fixed in less than a minute.
Wikipedia is pretty much self-sustaining at this point. Although vandalism is still rampant, it’s usually cleaned up before anyone bats an eye.
Therefore, my suggestion to you is to register on Wikipedia NOW, and then, four days from now, you can simply make these corrections as you see them. No need to report them – YOU will be among the many Wikipedians who continually upgrade and improve it.