How & where to invest?

Your question is open ended. There are many long-term investment options, but you should assess your risk profile in terms of investment amount and returns you expect to receive.

Equities have been the most preferred option for long term, however the risk is very high. You can invest in equity mutual funds that are somewhat able to withstand the stock market risk if invested via SIP. Debt mutual funds can give you decent returns with safety of principal compared to equities. So first create a goal and duration for which you want to invest and based on that select the appropriate option.

As per the market condition it is better to invest in debt fund, gilt fund like unit of NHAI , RECL RATHER than invest in equity shares or equity oriented mf, it is also advisable to invest in NPS for claiming tax exemption.