Hi Emiliano

Go to the floor tab--> choose a wall tool--> properties bar (right of the screen)--> click on the wall shape button--> select the shape (the second icon is a gabled wall)--> set the height and angles to fit your design
(see image attached)

In the example, I used a wall with gable, but if you wish to design just a gable, you can start using 1" or 1 cm

Lets us know if you need additional help

Patricia