Fail to import Design Studio Sample SDK Extension

I have the Design Studio 1.4 and am trying to import some sample SDK extension.

I followed the instruction in Developer Guide: Design Studio SDK.

I believe I already have 1.4SDK installed. There is no trouble for me to install the Eclipse IDE (step 3.1.3) and register the SDK XML Schema Definition (step 3.1.4).

However, I received error message at step 3.1.5: Importing a Sample SDK Extension. The error is shown below.

Has anyone meet this kind of issue below?