1. Install Active Perl
2. From the command prompt, type 'ppm'
3. from the ppm> prompt, type 'search excel'
4. Install any of the modules you see on the list by typing 'install n' (where 'n' is the number listed next to the module you wish to install.

You can also install a module "by name" instead of by search number. This is documented in the PPM documentation, included with Active State Perl.