Sometimes it is line-in on the laptop
, depending on age and make. If both present, use line-in.
has a neat signal monitoring screen
and the help file says how to use it for tuning. Tuning by pre-tones is very easy. It also says how to correct slant in early transmissions.
When tuning into the station you will hear, very distinctively, a series of pre-tones (beeps) that and later long chirps just as if you picked up a phone
and someone tried to send you a fax.
The set up can be tested with pre-recorded fax chirps from any source.
JVComm32 - sound samples
Listen to the HF fax sample, that's what you want to hear tuning into any wefax station.
PS Now you can receive NAVTEX transmissions too.