Inserting aluminium doors and windows

[Lumaja]

Ubuntu 12.04 LTS
Sweet Home 3D ver. 4.1
java ver. 1.6.0_45

Need to insert doors and windows the ideal will be with a frame 50 millimetres width the frame with two smaller fixed glass on the ends and a bigger sliding on the middle.
Looking in Doors and Windows found one fixed window and sliding window, insert the fixed window on the ends and the sliding on the middle, the middle window is much longer than the two end ones it looks more like a door nearly touching the floor.
Can some one explain how to changing the dimensions to make it shorter.
Thank you

[hansmex]

Please, read this section in the Userś Guide.

Hans