Unless you are fortunate enough to have a net worth sufficiently high to give you access to an individually managed account run by an asset management company, the odds are good that you are going to do most of your investing through mutual funds. There are three different ways you can purchase shares of a fund.
Through Your Broker
If you have a brokerage account, Roth IRA, traditional IRA, or another account with a stockbroker such as Charles Schwab or Merrill, you can buy most mutual funds just like you would stocks. The easiest way to do it is through the broker's website. Many online brokers offer free trades nowadays, including for mutual fund purchases, and they usually don't require you to have a certain minimum balance. You might also call or go to your broker's branch office in person and request the transaction.
In some cases, you may be charged a commission or a flat fee for the purchase. Such a charge is called a load. There are so many funds available that don't charge a load, you should really try to do your own research and find the right no-load fund for your current investment need, whether it's increasing your exposure to Asian stocks or seeking high-dividend-paying companies.
You should also keep in mind that your brokerage company might have a family of proprietary funds, or a network of funds with which it is somehow affiliated, that your personal broker might get an incentive to sell to you. You should carefully consider whether these proprietary offerings are the best options for you.
Directly From a Mutual Fund Company
If you know you want to have your money invested in a specific mutual fund or in mutual funds that make up part of a larger mutual fund family, you can often open an account directly with the mutual fund itself. You can initiate a transfer of funds online or fill out paperwork and mail it in with a check. You will also need to tell the company whether you want to open a regular account or a retirement account such as a Roth IRA or traditional IRA.
You can even set it up so that the mutual fund automatically makes investments for you by regularly withdrawing money from your checking or savings account each month. This periodic investing results in dollar-cost averaging and can be a helpful way to smooth out the average price you pay for your mutual fund shares and possibly help lower the risk that you will have put most of your money into the market at a peak, such as the day before the dot-com crash or the Wall Street meltdown that started the Great Recession in 2008.
The biggest advantage to buying fund shares directly from the mutual fund company itself is that you're unlikely to get charged a commission or fee, meaning more money goes into your investments and is working for you.
A downside of buying shares directly from the mutual fund company is that it can be more difficult to transfer your holdings later or diversify into additional securities, including shares of mutual funds offered by other financial institutions.
Through a 401(k) or Other Retirement Plan at Work
If you work at a company with more than a few dozen employees, you probably can sock away money in a 401(k) or similar retirement plan. In almost all cases, the main investment options will be mutual funds.
A downside of a 401(k) is that you are likely to have only a limited menu of potential mutual fund investments, some of which may be subpar. Nevertheless, if your employer matches a percentage of the money you invest from your paycheck, a 401(k) is often a wise investment option to take advantage of.