Several are saying "you need to be 18" which is true if you want your own account. But if you have a parent that you trust and believe would selflessly support you in this endeavour, then you can open a joint investment account with them. Even a Roth IRA, but you can't contribute more than your earned income... so you need a job. (I had a Roth IRA when I was 14, after I turned 18 I reassigned the account to just me). If you don't have a parent or guardian who matches this description, then go with a savings account and learning until you're 18.
As others said, definitely read first. I know you're excited to get started right away, but if you spend the next year learning about investing, then invest from 16 onwards, you'll still have about a 25 year head start on most, which will put you well into multi-millionaire status.
As far as books, I love all of the ones recommended by the side bar in /r/personalfinance, and also this one which is $2 for paperback or $3 on Kindle and only 100 pages and a really solid overview that draws from dozens of the best books out there.
I like all the suggestions from the reading list, but I also really like the book linked below. It's 100 pages, and is kind of a summary of all the great books on investing. Really boils everything down to it's essence:
https://www.amazon.com/Beginners-Guide-Investing-Money-Smart-ebook/dp/B005Y4JS0A/
It's great you want to start reading. If you read a book every two months on this... six a year, 12 in two years, you'll be a financial wizard and easily on your way to millionaire status.
I was looking through the beginner guide on the sidebar and the primary ones resources are amazon referral links.
this is the first link, a beginner's guide to investing http://amzn.to/1tYCeEw
Here's where the link goes https://www.amazon.com/gp/product/B005Y4JS0A/ref=as_li_qf_sp_asin_il_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=B005Y4JS0A&linkCode=as2&tag=194753847ws-20&linkId=EARINNG77PWDYL3A
ref=as_li_qf_sp_asin_il_tl is a referral meaning someone's making money off these links basically.
Which is shady considering the links are there to provide noobs like me w info, but it's actually just a link to buy a book.... So I'm left wondering why "refer to the sidebar" is any good if it's just telling me to buy a book...
If the purpose is to provide information, then you could remove the referral link! Here's a referral-less link to the same book! https://www.amazon.com/gp/product/B005Y4JS0A/
This is all you need to know. Its a short book. No app is going to teach you anything helpful about the stock market that you cannot learn from that short book.
I can summarize it, but it will teach you a lot more of the fundamentals and what all the terms and such mean.
What you'll do after you learn it: Invest in an ETF like VOO or a vanguard retirement target date fund. You can sign up for that at vanguard.com or a similar site.
Do not try to pick individual stocks, it is a waste of your time and will only lose you money in the long run (though almost half of people will do better in the short run because that's how random guesses work, and those people wrongly think they are great at it and do better than an ETF over time).
There is much less skill involved in investing than you think, as stock prices already take into account all the things you think make it more valuable. Even seasoned investors essentially just gamble around the average, which you will make with an ETF. Of course those seasoned investors do it with other peoples money and take a percentage of the money for it.
If you would like to learn more detail about how to value invest in a way that is not gambling, you can read this book instead. Its where Warren Buffet learned how to make money. It teaches how to find deals in stocks that the thousands of other professionals looking at them for thousands of hours may have missed. It is impossible to do without through business knowledge, a lot of money, and a ton of time pouring over financial documents of the companies you plan on investing in. Basically you need to spend even more time than those thousands of professionals.
Warren Buffet, btw, recommends that anyone without extensive business knowledge and a huge staff of professionals to look into these things invest in ETFs, since they are otherwise essentially randomly gambling in a way that loses overall.