You can invest in index funds (open-ended funds that track an index) but not in ETFs.
ETFs are Exchange Traded Funds, which means you need a demat account to invest. We do not support demat accounts , so you cannot invest in ETFs.
The terms ETF and index funds are often (mistakenly) used interchangeably. Not all index funds are ETFs, and not all ETFs are index funds (just because a fund can be traded on the exchange does not make it an index fund).