Hello Akuc007,
Dynamo Sandbox will run stand-alone without any Autodesk software if you don’t want to use Geometry. This blog post explains a little more about Sandbox.
If you want to use Geometry in Dynamo Sandbox (Which I believe is what you are asking) you will need to have a recent version of Revit, FormIt or Civil 3D. We typically support the most recent version and two versions backwards.
If you are looking for Geometry inside of Sandbox then please go to your manage.autodesk.com tab and install one of these applications 