Select Data Source is disabled under Substitute when try to add a data pool to project in IBM Mobilefirst Platform Test Workbench 8.7. I am having the same issue mentioned by @Rakesh Manusani in his question.
I Have followed the steps mentioned in below link. (http://www-01.ibm.com/support/knowledgecenter/SS2HS7_8.7.0/com.ibm.rational.test.lt.moeb.tutorial.doc/topics/ios_lesson7.html)
I was able to select the data pool to use in test
I am stuck in Step 6.b.
I right click on Username field in test script and select Substitute and get an option Select Data Source but it looks disabled
I am using MTW 8.7 and MFP 7.0