Placing railing

Using the railing tool, you can 
1. Add railing as free-standing element 
2. Place railing on an existing stair / ramp
3. Set up automatic railing placement when you create a stair / ramp

1. Create a railing by sketching the path for the Railing. The path can contain lines and arcs. Press ENTER to close the path. 
Optionally, click on any node to modify its elevation or press ENTER again to close the command.

Location: Building - Railing - Railing by sketch

2.  You can add a railing to an existing stair / ramp. The stair or ramp left or right side without railing is highlighted when you move the cursor over it. The railing will follow the stair path and elevation. 

Location: Building - Railing - Create railing on stair / Ramp

3. Open stair or ramp properties dialog. Click Railing button and railing styles panel appears. Select the railing style optionally for the left and right side.
The Regenerate checkbox can be activated when you modify an existing stair. The regenerate Railing feature restores the original Railing form deleting all eventual manual changes you did on it.
Location: Building - Properties - Stair / Ramp