The answer depends on the type of mutual fund. Exchange Traded Funds (ETFs) are closed-end funds that trade like stocks on one of the stock exchanges. You purchase shares in these funds through a brokerage account, just as you would for any other stock. Open-end funds are available from the fund's distributor, and in many cases through other agents such as brokerage firms, investment advisors, retirement plans, etc. You simply call up the distributor or agent and ask for a prospectus (which you must receive before making any investment) and the necessary forms to open a new account. After filling out the forms and sending in a check for the initial investment, you are done.