For the money in the beneficiary IRA, you should be able to pick from a group of Investments. This can include stock funds, bond funds, and even individual stocks. Those funds can be mutual funds or Exchange traded funds. It is likely among those lists of options some will be index funds, which are great because of their low costs.
If you have earned income from a job, you can use the minimum distributions that you are required to withdraw from the beneficiary IRA to increase the amount of money you are contributing to your IRA or 401(k). It won't let you exceed the limits set by the IRS, but if you aren't currently hitting those maximums, this required distribution can get you closer. Those additional funds can of course be invested in any of a large number of funds or other investments.
If your beneficiary IRA doesn't give you a lot of investment choices, you should look into rolling it over to a investment company that has a lot of investment choices.