Drag a second measure to Rows and Tableau draws a second chart under the first, each with its own axis. Right-click the second pill and choose Dual Axis to lay the two on top of each other. The second axis moves to the right side.
With two measures in the view, the Marks card shows All plus one card per measure. Open a measure's card to give it its own mark type, color or labels. Bars for one measure and a line for the other is the classic combination chart.
The two axes keep separate scales. When both measures use the same unit, like dollars, right-click the right axis and choose Synchronize Axis so equal values sit at equal heights. When the units differ, like dollars and a ratio, leave them unsynchronized and keep both axis titles visible.