This should be large enough to put the entire, ramen into without having to break it (you can break it if that is your preference). It should also be small enough so that water can completely cover the ramen noodles. Some people like to eat ramen wet instead of completely drained, so if that's the case, you can be more generous with the water. If in doubt, try 2 cups, but if you want more, that'll work, too. You can substitute some other liquid for the water, such as soy sauce, or broth, but water will work as well. On most stoves, you should just turn the knob as high as it can go and wait for the water to boil. If, during the cooking process, the pan starts to bubble over the top, just turn it down. Next time you make ramen, do not turn the stove on as high as it can go. So long as the water is bubbling, its temperature is at the boiling point and it is circulating.  A furious boil adds little and risks a boil-over, so feel free to turn down the heat a bit once boiling commences. At this point, you can do one of two things: you can pour the entire pot of ramen, including all of the liquid, into a bowl, and have a soup, or drain the water, and just eat the ramen.

Summary:
Get a big pot. Pour your preferred amount of water into the pot. Boil the water. Stir well.