If your young, inexperienced and unfit then I suggest that before you even touch your first piece of metal you work calisthenetics. This will have the following advantages:
-You will get significantly stronger
-You will get significantly more muscular
-You will learn how to "do" exercise, your motoric center will adapt to the new movements
-You will learn what form means, without the risk of busting your back or having to call someone else to pull weight off your chest
-Your muscles will also gain strength endurance, which is a quality required for lifting weight later on
You should do pushups, squats and pullups, be sure to pay attention to moving symetrically.
Remember that you now need more food and water than before, so eat eat eat. Later when you move out of your home you will see what a help it is to have someone else do the cooking and grocerie shopping.