import net.sf cannot be resolved

[Vikash Anand]

Dear All;
          I am new to ofbiz. I downloded Ofbiz and I tried to configure
OfBiz on Eclipse using (import project from existing workspace) on Windows
platform. I am getting 3 errors:
1. JSONObject cannot be resolved
2. JSONObject cannot be resolved to a type
3. import net.sf cannot be resolved

Please let me know where i am making mistake or what jar i am missing.

Thanks and Regards;
Vikash Anand.