Once you installed the SDK you can start the emulator from Start -> Programs but if you want to compile files and run the project you need to have PERL installed on your machine as a lot of build scripts are written in Perl. You can install perl from Gnu package or the easiest one is to install it from activeperl.com from below link:
http://www.activestate.com/Products/ActivePerl/ click on Download
Once the installation file is downloaded, depending on which OS you have click on msi or zip file to install the active perl on your machine:

The installation program starts. Choose everything as default until the installation is done:

Once the installation is done to check to see if everything worked fine you can start a Dos Prompt and type “perl –h”:

It should give you list of Perl commands:

If you don’t get this list something is wrong in your installation. Try to uninstall then reinstall or check your Path to make sure you have C:\Perl|bin in your Path (under Start -> Settings -> Control Panel -> System -> Advanced -> Environment Variable

Here below is what I have in my PATH:
C:\Symbian\6.1\Shared\epoc32\tools;C:\Symbian\6.1\Shared\epoc32\gcc\bin;C:\Program Files\Common Files\SYMBIAN\Tools;C:\Perl\bin\;%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;%EPOCPATH%;