Format chart elements.

Select the Side Wall of the column chart and apply Olive Green, Accent $3,$ Lighter $60\%$ shape fill $($seventh column$).$

Add the Linear Down gradient to the side wall.

Apply the same fill and gradient to the Walls element.

Select the Floor element and apply the same fill with no gradient.

Select the gridlines and format them with Black, Text $1,$ Lighter $50\%($second column$).$

Select the chart area and apply a Black, Text $1$ outline with a weight of $\frac{3}{4}$ pt$.$

Edit the values in cells C$10$ and D$10$ to display $22$ and $15.$

Close the Selection pane if it is open.