grant access via FBA to our external LDAP users

I've performed a db attach upgrade from 2007 to 2010.

In 2007, access was set up:

• sitename.internal.com - internal passthrough AD domain users
• sitename.external.com - external LDAP domain users via FBA

I need to do the same in 2010.

I have sitename set up internally and externally.

What do I need to do to grant access via FBA to our external LDAP users?

Thanks!

Scott