Here's the idiot question of the day - how do I lock my driver's side door?

Passenger side has the separate lock under the handle with the little cover, driver side doesn't (nor does it have one in the handle's button like I've seen). Is manipulating the handle "down" from the inside supposed to lock it? Were door locks another thing that was an option back then, that we take for granted now?

I was born about 30 years after my truck was made, so excuse my ignorance.