O2 Sensor locations
 

I have a 1996 Ford Ranger 4.0L, V6 4x2WD and have an OBDII code for bad o2 Sensors.
Since being a 'newbie at mechanical engineering', I don't know the location of these 3 sensors.
Can someone send me a diagram or picture of where and what to look for please. Also, do I
use a wrench, socket or what? Thanks for everyone who reads and responds to this post.

Do you know the DTC retrieved?
O2’s,, good ones,, are replaced quite often. There are many things/conditions that can add to a invalid code. Having the code/s helps with a direction to move..
O2s are easy to spot in the exhaust, both before and after cat.

Sometimes you can remove a sensor with a wrench, but there’s a special 6 point socket that has a long cut away side or window that allows for the sensors harness to exit through. The sensor connector is generally to large to pass through a wrenches box end, and most times to hard to get a wrench into tight access areas...

Thanks much, another project added to my list.

O2 sensor location by OBC code
 

There are two things that can be interpreted from the OBC code. Type of failure and which sensor.

Type of failures - Off top of my head there is heater malfunction, too low voltage, too high voltage, etc. In most cases the fix is to just replace the sensor.

Which sensor - They are defined by Bank and Sensor number.
Bank 1 - the bank where first cylinder is. On your engine Bank 1 is on the right (passenger side).
Sensor 1 is upstream (before the catalytic converter).
Sensor 2 is downstream (after the converter).

Bank 1 Sensor 1 and Bank 2 Sensor 1 are hard to get to. They are on the exhaust manifolds in the engine compartment.

Bank 1 Sensor 2 is easy to get to. It's on the top of exhaust pipe after the converter. You may have to spray with a nut breaker spray - PB Blaster is popular. I used PB Blaster and let it set a few hours and used a small hammer on an open-end wrench.

An old oil field trick is to use PAM cooking spray (canola oil) to break free nuts.

Bank 2 Sensor 2 - this applies only to dual exhausts with two converters. The 4.0 L has a "Y" after the two exhaust manifolds feeding the one converter, so you won't see a Bank 2 Sensor 2 code.

YouTube of upstream sensor replacement