Open a crafting table
Place 6 iron ingots in the left and right columns
Place 1 stick in the center slot
Take 16 rails from the result
Place rails on the ground to build the track
Use powered rails if you want trains to move faster
Use redstone torches, levers, or redstone blocks to power powered rails
Connect track pieces in a continuous line
Add curves by placing rails around corners
Use minecarts on the rails to travel