Directions to Angers and the
Centre International des Etudes Françaises CIDEF

First you fly from Chicago or Saint Louis  (just below Lake Michigan on the map) to Paris, France.  
Make sure your plane lands at the Roissy-Charles de Gaulle airport. 
On the plane, enjoy the meal.  Skip the movie.  Try to sleep.  If you don’t, your “jet lag” will be much worse. 

At Paris, you pass through customs and get your luggage.  You will need to have your passport. 
You will be able to change money or cash a travelers check.  
You might also want to buy a “telecarte” at a “tabac.”  (See Dr. Rosenthal's recommendations)
You then find the SNCF and take a train down to Angers (just above the "I" in "Pays de la Loire").
Go to any ticket window (“guichet”) which indicated “billets/reservations.”  
You will almost certainly be taking a TGV to Angers (they are lovely and fast, one hour and a half to Angers).  
In all TGV’s you are required to buy not only your ticket but also an extra-cost reservation for a specific train.  
You can ask for a smoking or non-smoking car and a window or aisle seat ([non] fumeurs/fenetre (window) ou couloir (aisle)).  The ticket and reservation will cost 274FF one way.  
Before you get on the train, BE SURE TO VALIDATE YOUR TICKET!  (Compostez-le!) by inserting it face up into one of the small orange machines with the green arrows until you hear the “punch.”  
These machines are located just before you get to the platforms (“quai/voie”).  If you don’t stamp your ticket you will have to pay a fine on the train!  
Your train will be posted by number and final destination (usually Nantes) on the big departure board about 30 minutes before it is scheduled to leave.  
Your ticket will show the number of your train car and the number of your seat.  See ticket for details. 
Relax.  You’re almost there.  
Don’t miss the stop in Angers!

If you cannot catch a direct TGV link and have to go to Montparnasse, you can take the free shuttle bus to Terminal 1 and then the regional express train RER to "Denfert-Rochereau" (55 FRF). From there you take the metro (direction "Nation") to Montparnasse station.
Another possibility, especially if you have a lot of luggage, is the Air France shuttle bus from Charles de Gaulle Airport to Montparnasse train station (70 FRF). Be sure to check with the driver in order to take the right shuttle. These shuttles operate every half hour from 9 a.m. to 2 p.m. and every hour from 7 to 9 a.m. and from 2 to 9 p.m.

Angers is right on the Loire river between Nantes and Tours

At the gate d’Angers-St. Laud you will be met by your host family or by someone from the CIDEF.  
Make sure you have arranged this with your family by letter well before your departure.
If you can, it is a good idea to go into the bookstore at the station and buy a map of Angers (un plan d’Angers—not a “carte”).
Here's a "plan" of the city.

The "gare" is on the Rue Denis Papin.
The University is in the V between the Rue Volney and the Rue Rabelais
(not at the red star, which is the Ecole des Beaux-Arts or Fine Arts School)
 

Thanks to Dr. Rosenthal for the travel recommendations.