Who_dat, welcome to this wonderful hobby!! As already suggested t's a good idea to begin by looking at lots of inspiring photos of other layouts, to get an idea of what you want to do. But I suspect you may want some specific information on the steps of building a model railroad, so here goes. I should mention that you don't necessarily have to do things in this order. MRRing is a hobby where there are always many different ways to do things.
1. Make a track plan. Once you get tired of watching your train(s) run around in an oval, you'll need a track plan. Fortunately, there are probably hundreds of track plans designed for the 4x8 sheet of plywood. One source of downloadable plans is the Atlas website:
http://www.atlasrr.com/
2. Track laying & wiring. There is a wealth of advice here on the Gauge, in books and on the net as to how to do this. Or, you can just start a new thread and ask.
3. Scenery & Structures: this includes all those things we do to make our sheets of flat plywood look like rolling hills, mountains, prairies, towns, cities etc. and the buildings, both of a scenic nature and the businesses/industries our RR serves. Again, information is readily available. Some people like to build kits, others like to create their own - scratchbuilding. Scenery materials can be purchased, but many can also be adapted from natural materials like branches, sand, rocks etc.
And finally a little piece of advice that has helped me a lot: don't let the magnitude of any task overwhelm you. Just do a little bit each day, and before you know it you'll see some real progress.
Good luck, keep asking questions, and keep us posted with your progress!
Val
