Fishn50 gave you great advice.
Browse the orvis fly patterns on-line to get a sense of different flies and identify some of the mysteries in your box.
I'd do a couple of things while you're looking:
For dry flies
What's the construction style? (traditional "Catskill style" hackle collar (Adams, Blue Winged Olive, Hendrickson) vs parachute hackle collar (Parachute Adams, Para BWO, Para Hendrickson) vs deer hair "arc" wing (comparadun, X caddis, Sparkle dun), and whether it has upright wings (mayflies) or downwings (stoneflies and caddis).
Where will it sit on the water?- in the film like parachutes and comparaduns or flies with clipped hackle on the bottom (thorax flies) generally used in slower water for picky fish, or ride high on it's tippy toes like wulffs with a heavy hackle collar that are easy to see, and float like corks in fast water.
What is the color scheme for different patterns? For instance you'll see that sulphurs are generally yellow with pale gray wings, but you can have Parachute, Thorax, Comparaduns, Sparkle duns (with a "shuck" of antron instead of a tail), or "catskill" style Sulphurs with a hackle collar
After a quick browse you'll be able to identify different "styles" of flies and have a pretty good sense of color schemes.
As far as references, anything by Dave Hughes is great.He has a great writing style and explains things very well. Depending on what you'd like to know,
Essential Trout Flies (An excerpt from his "Trout Flies" book which is also excellent but more expensive, with more info)
Amazon.com: Essential Trout Flies: Dave Hughes: Books
Handbook to Hatches
Amazon.com: Handbook Of Hatches: Introductory Guide to the Foods Trout Eat & the Most Effective Flies to Match Them: Dave Hughes: Books
And, here's a Hatch Chart for SE MN. It's not the most user friendly, but it will give you an idea of what to look for on the stream, and when hatches of different critters tend to happen during the year, and their typical sizes. ("sedges", "grannoms" and "speckled peter" are all caddis. For caddis you typically don't have to go crazy with exact matches, but having some in dark and light tones in a scattering over the range of sizes can help)
Hatch Chart pg.1
The web is also great for info. If you hear about a hatch like sulphurs and want some tips you can do the google thing and type in some like "fishing the sulphur hatch" and get tons of info on patterns, time of day to look for them, and other tips..
hope this helps a bit, keep asking questions!