You kids, now-a-days, have no idea what you missed out on. In elementary school Oregon Trail was, totally, the coolest! I was pretty excited to find a copy of the game, here, for download. Enjoy and happy settling!
(You know, I don’t think I’ve ever seen that end screen… ah, the attention span of a first grader!)
You need to supply yourself at Independence and then take off. You can buy supplies at all the army forts on your way (if you reach them), and the prices will rise depending on the distance covered away from “the civilization”. You can also trade things with the people on the way, you can just buy something from them or try to trade, but there’s never a guarantee that they’ll have what you need.
On the way some hardships can happen, so make sure you get enough rest and keep an eye on the food supply. You will have to buy, trade or hunt for food (some areas are better for hunting than others). I have to warn you though not to hunt too much, because you can’t carry more than 200lbs of food per hunt, the rest is left to rot (so if you get a buffalo you can pack up and go on – because it always weighs way over 200lbs).