I have installed HDP 2.5 and I am able to login into sandbox in cent using root uname and hadoop password but how would I start working with hadoop components like pig,hive and all, Do I need to install all hadoop compnents and configure it or it is configured and installed by default? How would I get a prompt of pig, hive spark, scala and all? also I am unable to login into Ambari using admin/admin uname password?
To learn how to start all those tools CLIs, in the same place you went to download the sandbox (https://hortonworks.com/downloads/#sandbox), you can see a link for tutorials: https://hortonworks.com/tutorials/
That's the best place to start with. Also, search through similar questions in HCC.