Instructions
Open Roblox Studio and build a humanoid model by arranging geometric shapes in whatever configuration you desire. Highlight your model.
Add a head to your humanoid model by adding it from the shapes menu. Humanoids must have a head, because features such as chat and health bars are tied to an object's head.
Click "Enter" in the Roblox Studio, followed by "Object," then "Humanoid." The Humanoid attribute should automatically attach itself to the model that you have highlighted.
Save your model.