There are some things you need to know in order to succeed at investing, even as you dip your toes in. For example, it won't be helpful to talk about financial ratios or valuation multiples unless you have a foundational understanding of accounting and finance.
Whether you're majoring in business or not, you should try to take as many introductory courses as you can (intro to finance, intro to marketing, etc.) These courses will give you depth that this resource won't provide.
However, this section will provide you with shortcuts and high level resources. If you've already taken a bunch of business courses, much of this will be review. But if you haven't, this section will give you the basic tools to move on to the other sections.
Starting Point
What is Capital?
Financial Statements
Income Statement
Balance Sheet
Cash Flow Statement
Financial Analysis