Your starting point is your e-mail address. You can very simply access it through the webmail interface.
Firefox 3 might complain about mis-matched security certificates, which is fine. Once logged in, double-click e-mails to read them, and drag-and-drop them in your folders.
You can change your password and alter a few settings at the mailbox settings page.
Your e-mail client (such as Thunderbird) needs a little information so it can fetch your mail. Always use:
sub3.homie.mail.dreamhost.com
Sending messages is done over the SMTP protocol. Make sure you are using SSL encryption and check that the port is 465.
Receiving messages is done either one of two ways:
SSL encryption and check that the port is 995.
SSL encryption and check that the port is 993.
More information is available here, here, and there.
Thunderbird 2 is known to complain about certificates (bug #228684); if so, you can use the Remember Mis-matched Domains extension.
For instant messaging, menopresto uses Jabber, an open protocol – so you can chat in real time with other acquaintances. The chat feature in the Google accounts is compatible with Jabber (whose real name is XMPP).
Your Jabber account has the same name as your e-mail. Just login with a program such as Pidgin.
You can have your own webspace at http://you.menopresto.net/. Olivier can install the Wordpress blogging software there for you, but you can also set-up your own schmingy yourself. This project started like that.
If you want to push things further, you can also register your own domain (something like betterthanmenopresto.net), and plug it into the hosting at menopresto. It costs $10 per year though, and a little more for European domains. Talk it over before you do anything.
In case you struggle, share the fun with Olivier.