This eight-minute clip from PBS NewsHour does a pretty good job of synopsizing when people need to know about investing:
An even shorter version would be to invest as much as you can in a tax-sheltered retirement or college savings account, preferably one offered through your employer if available. Roth IRAs are a good choice for retirement accounts. The best thing to hold in the account is usually a low-cost index fund that invests in a broadly diversified set of investments, such as a target retirement fund. Especially if you invest outside a retirement account, an exchange-traded fund (ETF) is usually a good choice and can have tax advantages.
Besides long-term investing you should have short-term savings, ideally enough to live on for six months or more, plus a down payment if you’re hoping to buy a house. Pay off credit cards. Otherwise you’re just giving away money to a bank. Borrow money only to buy a reasonably safe asset such as a house or a (not too expensive) car you need to get around.
Actually, there’s more to it than that, including how to avoid scams, including from your seemingly friendly bank. The advice in the video is good, but you ought to spend a little time reading about personal finance from mainstream authors. Just be sure to avoid get-rich-quick schemes like the “Trump University” scam.