It very simple to do, I also had the same issue many times.
Please go through the following blog
Thing to do : Change the default Password(i.e. hadoop) :
Usually, sandbox prompt to set you new password if you login into Sandbox for the first time. If the password changing prompt is not coming please do the following
Just use the ALT+F5 in splash screen => enter root/hadoop as use name and password => type passwd (to change the password of root user) => write two times the new desired password you want.
And use the same password into any client like putty/MobaXterm or you name it. (all the connection details will be the same port is 2222 and host would be localhost/127.0.0.1 will work)
Hope this would help.
# Referencing words #
Splash screen is look like this
