The Yocto image used in Edison doesn't use apt-get as package management command. It uses the opkg command instead. This means that you have to use the opkg command to install packages. In the following thread you will find an opkg repo for Edison, it might be interesting for you: Edison opkg package repo created
Additionally, the Yocto image doesn't include all the packages that you would find in a regular Linux distribution, for example Ubuntu. Actually, Yocto is not a Linux distribution itself, but it allows you to create one for you to be used in embedded applications. If you need a package that is not included in the default Yocto image, you could install it (through the opkg package management command). In the repo I mentioned above you will find useful packages. If you need a package that is not listed there, you can post a request for it in that thread.