Three ways to do this as mentioned in this answer.
Index funds are a low cost and ‘passive’ way to invest in the entire basket of the stock market. There is a lot being talked about passive investing these days. We believe that in the Indian market, there is significant room for well managed mutual funds to give a much higher return than the index. Our picks have given about 5% extra above what the index has given over the last 5 years. This should continue for another 5 years atleast and can mean a higher corpus for you.
The best way to start an SIP on any index mutual fund, is to buy it from a direct mutual fund platform that has the best advisory support. The advantages it gives you are:
1. Access to the best selection of funds, both index and other active funds giving higher returns
2. Direct Plan Index Funds give higher return on any mutual fund since they carry zero commission. A monthly SIP of Rs 10,000 for 25 years gives you a corpus of Rs 81.3 lakhs in a Direct Plan Index Fund vs 73.8 lakhs in the regular plan of same fund. See the fund snapshot below for Reliance Index Fund Nifty plan.
3. Best advisory support if needed from someone trusted (and SEBI Registered Advisor) since they dont make indirect commissions out of your investments.