How do you ease a tween with an armature?

Click on a frame between 2 keyframes in the span and in the Properties Panel go to the Easing section and select Stop and Start from the Type drop-down and then drag the Strength slider to the left so it's at -100.

I know it seems counterintuitive based on the naming of things. I wish we just had thumbnails of curves that represent the easing and by clicking on them it applies the ease type. But for now try and remember Stop and Start and you have slow, medium and fast to choose from and then the strength slider. Don't ask me how strength differs from slow medium and fast tho LOL