Choose where you want to go and locate the El station nearest to that location, as well as the one nearest to where you are. You can do this by using a train map, asking an attendant at a nearby station or by using the "Plan a trip" option at www.transitchicago.com
Enter the station (it may be underground or above ground, up some stairs) and look for the turnstiles that accept your fare. The El trains do not accept cash, so you need to have either your Chicago Card (available online and connected to your credit card) or a transit card. If you don't have either card, see Step 3. If you do, skip to Step 4.
Find the ticket dispensing machine (usually located near the turnstiles) and insert your cash to claim your ticket.
Put the transit ticket into the slot on the turnstile, wait for it to come back out, and go through. If you're using a Chicago Card, wave it at the Chicago Card reader on the front of the turnstile.
Locate the signs for the direction that you're traveling and stand on the correct side of the platform. If the train is above ground, you may need to access it with a specific set of stairs or elevator. If it's below ground, you will likely be able to stand in the middle and just make sure you get on the correct train when it arrives. The direction each train is traveling will be located on a sign above the platform as well as on a sign in the front of the train's window.
Board the train, find a seat and enjoy the ride.