"I am new to this, don't criticize me."
Well Missy, How about constructive criticism? You don't even know the correct terminology! To really know what you're doing there's a lot to learn such as the relationship of power output of stereos and amplifiers to the power-handling capacity of speakers, the electrical resistance of speakers (called impedance, measured in ohms), the importance of impedance matching and the effect impedance has on power, the effects of different speaker wiring configurations on impedance as governed by "Ohms Law", the relationship of the power drain on your cars electrical system and the ability of your alternator to supply enough power, and some of the basic audio physics governing power vs loudness. And that's not all.
It's all fairly simple, really, but to a newbie it can be overwhelming. One problem is that there are plenty of people out there willing to give advice that think they know what they're doing but don't have a clue. This forum is no exception. Boyfriends are famous for "helping" with disastrous results for the car, or the equipment, or the relationship, so be careful who you take advice from or let work on your audio system.
To cut to the chase, except for adding a subwoofer (which requires an amplifier), you don't need to add any speakers because it can get complicated and you don't really need them. More speakers won't make a system louder without more power. Adding speakers alters the impedance (ohms) of the system. It will either raise it (if wired in series), reducing the amount of power the speakers each get, or it will lower the impedance (if wired in parallel) which your stereo might not be able to handle, requiring you yo know the specifications of the head unit. So, I suggest that you simply replace what's already there. Factory speakers are usually pretty low quality, so it's the best thing you can do to most car audio systems. After that, you might want to amplify them, and / or add a subwoofer, but one thing at a time.
Your base model Altima should have two 6.5" diameter front door speakers and two 6"x9" oval rear deck speakers. The front doors can also take 5.25" speakers and all they need is an inexpensive bracket. Here is a video on how to replace them: https://www.youtube.com/watch?v=8FbucYc8O4I You'll see that it is pretty involved and the rear speakers are even more complicated. See here: https://www.youtube.com/watch?v=9ILNhGHQueU
So let's stop right here and say that for many people, probably including you, that professional installation is the best way to go and worth every penny. Any reputable shop also offers a warranty, so if there are any problems within 6 months or so afterward, they'll fix it. All you have to do is select the speakers you want and they'll do the rest. Select from any of the good brands (JBL, Infinity, MTX, Kicker, Alpine, Pioneer, Rockford, JL Audio, Altec, Clarion, Diamond, Sundown, etc) and stay away from the cheap ones (Crunch, Krakow, Jenson, Pyramid, Soundstorm, Boss, Power Acoustik, Rockwood, etc)
(p.s. Did you draw your own Avatar? Not bad. )