most of the installs I have seen have a file in a .img format
You need to get a program that takes the img format and puts it onto your SD card in the fully expanded way.
Look for an imaging program that works for you. I used windows to image my cards.
power supply: this was a huge issue for me and took two days and numerous power supplies to overcome.
You can't assume a "5v" supply is giving you 5v. I had many that didn't meet the threshold of 4.72v. Most of the failures were samsung power supplies for phones or tablets. (I love samsung, don't get me wrong)
I eventually found one that worked (a motorola supply).
If you haven't done it yet, invest in a voltmeter. Its an indispensable piece of equipment that you will use for decades to come.
By measuring the positive lead with the red wire and the negative lead with the black wire you can determine the output voltage of your supply. If your reading is negative, then you have the polarity wrong.
It doesn't have to be anything fancy. The cheapest off-the-shelf voltmeter will usually do both AC and DC voltage, ranging from mv to thousands of volts.
They are pretty hard to fry, but other electronics (including the rpi) are very easy to fry.
keep at it man. 15 is a great age to start. It might seem hard, but keep whacking at it, persistence pays off.