There are two lines to edit I believe.
You need:
[Station]
station_type = Interceptor
...and a bit lower down you need:
[Interceptor]
device_type = ecowitt-client
...but there is a lot more you should configure if you just read the weewx.conf file you'll notice that there are plenty of other things to fill out...especially in the [Station] section. It isn't a requirement for it to work ....but you'll want to do thing like Lat/Long, elevation...etc.