Assuming you have combo dsl modem+router (most dsl users do, but not all):
[dsl modem+router]<-- wire -->[lg bd300]
If you want wireless, obviously you'll need to add a wireless router/AP. And since I believe the lg bd300 doesn't support wireless either natively or by the addition of wireless adapters, you'd have to use a wireless ethernet bridge:
[dsl modem+router]<-- wire -->[wireless router/AP]<-- wireless -->[wireless ethernet bridge]<-- wire -->[lg bd300]
Then just open your Netflix account, connect to the service through the lg bd300’s Netflix interface, and enjoy.