Character week begins with the APEX Scene Animate SOP. This will be very new for many people. Don't worry - this node can be used with existing rigs that come with Houdini or are in the Content Library.
Here is another tutorial that uses that node: How to Pose and Animate Electra [www.sidefx.com]
This lesson uses the Electra rig which comes with Houdini. You can also use other characters found in the Content Library [www.sidefx.com].