One of the things that we ask you to do in this course a lot is to install software from various places. However, if you use OS X Mavericks, you may notice that the default installation has a couple of security settings that prevent you from just installing software from the web. This is meant to protect you from installing kind of bad or malicious software. But it can also prevent you from installing things like RStudio and other pieces of software. So in order to change the settings, it's fairly simple. You go to the Apple menu here, and you click on System Preferences, and then you want to go to Security & Privacy. By default, you won't be able to make any changes unless you type in your kind of administrator password. So I'm going to click on the lock here, type in my password, and now you can see that there are a number of options here for downloading and installing apps. So, the safest option is to only allow applications from the Mac App Store, but there are many things that you'll need to download for this course that aren't in the Mac App Store. So you need to click on the Anywhere button. That will allow you to install software from the web or from anywhere. And it's your responsibility to kind of make sure that the software is okay. And so you'll need this to install things like RStudio and GitHub and other pieces of software. So, that's how you do that on the Mac.