I would do the following:

1. Read the SOAP::Lite documentation. (which mentions 'Limited support for WSDL schema.'
2. I would notice that the 'AVAILABILITY' section mentions another website (why it's not under 'SEE ALSO', I have no idea): http://soaplite.com
3. I would read said website, especially focusing on the Guide (such as Access with service description (WSDL)) and the Cookbook.

If I ran into a lot of trouble, I'd probably also look into SOAP::WSDL and read the WSDL spec.

I'd get very confused by it, so I'd go out and get a few books to read, such as Programming Web Services in Perl, and Programming Web Services with SOAP

I'd then get really annoyed at how interoperability among different toolkits with SOAP is a complete load of shit, and get fed up with the issues of trying to deal with complex types, and what they refer to on the SOAP Builders mailing list as 'impedence issues'.

I'd then spend a month or so digging through SOAP::Serializer (part of the SOAP::Lite module) until I understood what was going on, and write my own custom serializer.

(at least, that's what I did when I had to learn about WSDL)

Update: Minor correction -- that's not exactly what I did, because SOAP::WSDL wasn't out when I had to deal with these headaches. It's possible that it might've saved me a whole lot of time