Ignition switch is under the steering column above brake pedal.
It is a slider switch.
Key switch on the steering column is connected to the ignition switch with a long bar/rod.
When you turn the key the bar moves and slides the ignition switch into it various positions:
ACC, OFF, RUN, START
If key is hard to turn or doesn't always turn when key is inserted, it is most likely the key cylinder is failing or your key is too worn down to push pins inside into position.
Google: ford ranger ignition lock cylinder replacement
For ignition switch itself, Google: ford ranger ignition switch replacement
Most years are the same and most manufacturers as well, so outside of the specific parts involved any "how-to" will be helpful