You have to invest for various needs like future goals, Tax Saving, etc.

Where should I invest?

You have to invest in different asset class as per your future goal horizon and your risk appetite. Equity, Debt, Real Estate, Gold are the examples of different asset class. You have to choose right asset allocation among them.

When should I invest?

You have to start investment once you start earning. Investment is nothing but power of compounding. A small amount invested in early stage can create huge wealth compare to a big amount invested in later stage.