To open the about:config page, type about:config in the location (address) bar and press the Enter key, just like you type the url of a website to open a website.
If you see a warning then you can confirm that you want to access that page.
Thanks, I have double-checked the settings you suggested, and recent history is still blank. I've attached screenshot of my settngs. I tried to visit the link, but The requested URL could not be retrieved While trying to retrieve the URL: http://kb.mozillazine.org/browser.history_expire_days The following error was encountered: * Connection Failed
Did you check the setting of browser.history_expire_days ?
That pref determines what is actually kept as history in places.sqlite and overrides browser.history_expire_days_min, which specifies what is kept in memory for quick access.
If the MozillaZine KB site is having problems then try again at a later time (seems to working fine now).