To install Client Hyper-V, you use the well-hidden Windows Feature control panel. (Thanks to the wonders of Start Search in Windows 8, however, it’s easily found if you know what you’re looking for: Search for windows features, filter to Settings, and select Turn Windows features on or off.)
Expand the Hyper-V entry and you’ll see two sub-entries, Hyper-V Managements Tools and Hyper-V Platform. If the second is grayed out, you can’t install Hyper-V. (That said, you may need to turn on virtualization features in your PC’s BIOS or UEFI firmware first. So check that before despairing.)
Select the features you want to install, click OK, and Client Hyper-V will be installed. After a reboot you’re good to go.