Locking the hubs

My boyfriend has just inherited a 1990's Jeep Sahara and I am about to
take it out to a friends house that really does need 4wd for about the
last half mile or so. I can walk it if I can't figure it out, but I was
wondering if someone would explain to a complete newbie without a
manual how I engage the 4wd and lock the hubs? I have done some
research online and have some small idea of how to do it, but there is
nothing as to actually WHERE or what mechanism I use to engage the 4wd
(I assume it is the lever on the gear shift?) and where I unlock the
hubs?

Apologies from the ignorant...