Select Render Walk → Measurements from the side menu.

Select the room you want to add measurements to and click the "+" button on the top right.

Measurements - select room and click + button

Now drag the points to indicate the measured distance, then click Save.

Drag measurement points to set start and end, then Save

Now you can modify the appearance of the drawn measurement, add a label, and change the size, shape and color of each point and line.

Measurement style editor - customize label, color, size

Click Save.

You can view a live preview of measurements in this demo.