If you searched using 'search' option, you will be getting multiple results as shown below. From that, you just note the serial number for the module which you required and just type that number as shown below

ppm>search wwww::mechanize
  1. WWW-Mechanize            [0.72] Handy web browsing in a Perl obje
+ct
  2. WWW-Mechanize-FormFiller [0.05] framework to automate HTML forms
  3. WWW-Mechanize-Shell      [0.19] A crude shell for WWW::Mechanize
[download]

After this, if you want to install first module, type install 1.

or even simply,

Also take a look at holli's excellent node A guide to installing modules for Win32