Investors can buy or sell shares of companies within the Dow Jones Industrial Average (DJIA) through standard stock trading platforms, such as brokerage accounts, robo-advisors, and financial apps. To purchase shares, investors must first select a brokerage, open an account, and fund it. Many brokerages now offer commission-free trading, making it affordable to buy shares of DJIA companies without incurring additional costs.

Once the account is set up, investors can search for individual companies listed in the DJIA, using their unique stock symbols. The DJIA includes prominent blue-chip companies, so these stocks are usually highly liquid, allowing easy entry and exit at any time during trading hours. Investors can place either market orders to buy or sell at the current price or limit orders to execute trades at a specific price level.

Exchange-traded funds (ETFs) like the SPDR Dow Jones Industrial Average ETF (DIA) are a popular option for those interested in diversified exposure to the entire DJIA rather than individual stocks. By purchasing shares in such ETFs, investors gain proportional exposure to all companies in the DJIA, simplifying management and diversification. Both direct stock purchases and ETFs provide accessible avenues to invest in the DJIA.