You have the option to install all available versions of Internet Explorer at once, or install only specific versions. To install specific versions, you'll need to run each command separately.
Copy and paste the command(s) below into Terminal and press Enter. Don't include the commented (#hash) portion. You'll be prompted for your OS X password.
# Install all versions (Internet Explorer 6-11):
curl -s https://raw.githubusercontent.com/xdissent/ievms/master/ievms.sh | bash
# Install only Internet Explorer 6:
curl -s https://raw.githubusercontent.com/xdissent/ievms/master/ievms.sh | IEVMS_VERSIONS="6" bash
# Install only Internet Explorer 7:
curl -s https://raw.githubusercontent.com/xdissent/ievms/master/ievms.sh | IEVMS_VERSIONS="7" bash
# Install only Internet Explorer 8:
curl -s https://raw.githubusercontent.com/xdissent/ievms/master/ievms.sh | IEVMS_VERSIONS="8" bash
# Install only Internet Explorer 9:
curl -s https://raw.githubusercontent.com/xdissent/ievms/master/ievms.sh | IEVMS_VERSIONS="9" bash
# Install only Internet Explorer 10:
curl -s https://raw.githubusercontent.com/xdissent/ievms/master/ievms.sh | IEVMS_VERSIONS="10" bash
# Install only Internet Explorer 11:
curl -s https://raw.githubusercontent.com/xdissent/ievms/master/ievms.sh | IEVMS_VERSIONS="11" bash
Troubleshooting
If you run into any permissions-related issues, you can run the command using sudo (super user) by prepending each command above with sudo.
If you have any issues running the "Install all versions" command, check to make sure you have the latest version of VirtualBox and, if you still have issues, try installing each VM separately instead.
If you run into an error similar to VBoxManage: error: Appliance import failed or 'Win7/IE11 - Win7.vbox' already exists, try this solution.
A note on Windows 10 Internet Explorer Edge
The "Install all versions" command will also attempt to install the Internet Explorer Edge version -- this is the absolute latest release of IE. However, installation using this method is unreliable, so if you see an error at the end of the script you can safely ignore it (unless you want the Edge browser, of course). If you really want the Edge version, you'll need to do a bit of troubleshooting of your own.