it's in the box on the right inner fender. first one off the bat.
you can go here,
http://www.autozone.com/autozone/homePage.jsp
it's a free online manual only. just sign up, plug in vehicle info and go to,
REPAIR INFO / 1989 TOYOTA TRUCK PICKUP 2WD (4 CYL) 2.4L FI 4CYL REPAIR GUIDE / CHASSIS ELECTRICAL / CIRCUIT PROTECTION / FUSE AND CIRCUIT BREAKER APPLICATIONS
fig 4 has the location and position of all fuses and breakers on the truck. it shows the location of your horn fuse.
owner 93 toy pu