What kind of "populate"? A one time data import or periodic updates?
Don't know anything about WordPress, but you should be able to set up some kind of records import that works. I'd investigate the following options in the following order if I were in your place:
Import via ODBC connection to the WordPress tables (need a driver that works for WordPress)
Other typical data file imports such as CSV or Tab delimitted files genarated by an export from WordPress.