Can find out where your polling place is from the second link, then on election day you go there, fill out the ballot and you're golden. First link has detailed info on how to vote, with links to documents detailing it.
If you can't go on election day, there are ways to register for absentee ballots, I'm not sure exactly how that is done, but can certainly do it. You could also ask some of your coworkers or your boss what the policy is at your job on that, I think a lot of places will let workers take some time to go vote... but then maybe I'm spoiled, what with working for the government and such.
If I'm crazy on the state and you're elsewhere, let me know and I can look up info for where you want. If you'd like, can maybe chat on AIM some evening and walk through the automated website if you're having trouble.
Also, if I'm right about you being in Missouri, might be interested to know that Missouri is shaping up to be a battleground state this year. Meaning each vote has the potential to actually matter in the presidential election. Latest poll average for the state has Obama up by .3%, and he's been trending positively of late so he might be up by a point or two. But certainly going to be a close election, and you have the potential to actually change the outcome with your vote. Missouri has 11 electoral votes, so that could be important.
And, of course... it's always important to vote for your local representation, to make sure accurately representing your values and views. Think we've seen of late that the House and Senate are both important.