1. Draw a room to define the form and dimension of the area.
2. define it as a terrace/balcony/patio
3. Then change the property to the dwarf.
4. Put Railings if you want.
Remember only the railing elements that can be recognized as "windows" will be adapted automatically to the dwarf.
If you want pure railings without dwarf, put the dimension to 0.
5. Drop products from the public library and decorate your balcony/terrace/patio.
6. Go to Render and get your work