I have just bought a 1995 Jeep Cherokee Limited 1995. Bought by the heart

Can someone help me with the gear changing. With the small lever.
2wd = fine
part time 4wd = Part time light on on the dash
4wd = drive the car and then the picture of 4wd on dash.
All is ok so far.
How do you get it into 4wd low.
I have put the the auto in neutral and pulled back the leaver, this now makes the part time light to appear on the dash. Does not appears to be in low, driving forward ect no change (sometimes the 2wd light disappears for a second or so)
Was doing this on a gravel track to test
Am I doing something wrong
Thanks
John