Inside the QuickStart is written so
1. Import uFlex package
2. If Standard Effects package already imported - & gt; The delete uFlex/Standard Assets folder (ImageEffectsBase required for point sprites rendering)
3 In the Edit/ProjectSettings/Time decrease the FixedTimestep to 0.01 (the lower the better, but keep it adequate to the hardware "capabilities)
4. In the main toolbar select Tools/uFlex
5. If missing, the Flex GameObject will be added to the scene
6. Select the body type
7. If it Rigid and Soft or Inflatable pick a CLOSED input mesh
8. Click the Generate

But I test here, in the fourth step is to not bottom go to, how to order toolbar "uFlex" out "Select body type", I guess there should be a window here, don't know how to generate an object