You dont need to know everything at once, and can learn over time. I'd keep it really this simple:
1. Don't invest until you have paid off all debts (other than a home mortgage), have an emergency fund in place,
2.Open an account in vanguard, and put your money into index funds. Do not invest in more than 3-4 funds to start.
3. Use the vanguard calculator that the last poster used to determine how much of your money you should place in each fund.
A few things to remember:
-Only check your balance every few months (probably every 6 months is best).
-Read about IRA's Roth IRA's 401k's. These are basically accounts that you can put your money in to avoid taxes. If you dont understand them in your first year of investing its not a big problem, but you will want to start utilizing them soon.
-Only invest money that you won't need for at least 5 years. Dont worry about small or large fluctuations in value. Over time it will go up.
-As you learn more you might want to make adjustments to how much you have invested in each fund, but at the beginning it only matters that you start investing. Don't sweat or overthink the small stuff. Most people on this forum overthink a lot about their investments. In reality keeping things very simple and changing them rarely is the best strategy.
Good luck! You will do great. I started investing when I was in my teens and didnt really fully start researching it until many years later. Thanks to just blindly putting money into mutual funds when I was young and forgetting about it I am a lot richer now than if I would have hoarded cash.