This is by 1976：

first, you need an account that can do so.

Because all the investment has risk, and not fdic insurced (www.fidc.gov), so your normal saving account, checking account can NOT be used to hold a mutual fund (or a stock). (becaues your checking and saving account guarantee not to lose your money, up to a upper limit).

Many banks, online brokers have "investment account", or "brokage account". Open these kind of account and put your money in them allows you to buy or sell stocks, mutual fund.

If you know you only want to buy a certain mutual fund, many brokers allow you to open one special account for that mutual fund only.

Good ones include:

www.Vanguard.com
www.troweprice.com
www.fidelity.com
www.Schwab.com
www.scottrade.com
www.etrade.com

In which, the first three also provides mutual funds of their own (think them as mutual fund factory to make the fund). If you are new, I suggest you start with the funds the first three provide.

Please note, differet brokers may have different trascation fee/charge for the fund. And different funds may charge different maintain fees, etc.

我在fidelity的账户是专门为Roth IRA开的。免费，没发现有什么fee。