Alright, so you want to make maps with torque constructor? You should know a bit more after this tutorial.
The boxes here are different views of the map, I wrote in where they're viewing from.
Press the circled button, this allows you to create a box. Click it once, and click and drag where you want it.
Do this to make the floor of the box. Then click the button again to finish it. Continue making boxes until you make a room box thing as shown below.
You need to use multiple boxes to make it. Also, you may notice that yours looks different. That's because you never put in your textures. Make a folder with the images your would like to use as textures, they must be something like 512x512 pixels, or any other power of 2. (IE: 16, 32, 64, 128, 256, 512, 1024, etc.)
Click the browse button circled, a window should come up.
Press the button I marked 1 and name it Blockland or something like that. THen press the button I marked 2 and find and import the folder you made with the pictures. Now you can click the current texture drop box and choose one from the album.
Now go into the Modify menu that is circled and click he button I circled.
Now click two units from the center on one side, click the button again, and do it on the other side.
Now click that button again, click where you want the door's top, then enter 90 where I did, then activate, click the slice button again.
Select the box that is covering the door, then either delete it, or click the circled button. If you click the circled, it will turn pink, this is normal. It won't appear in game.
Now go to File > Export as Legacy DIF. Export it, then put the .dif file and the pictures in your map's zip folder, place it in mission editor. THere you go! you made a quick map. If someone can redo this for better clarification, please do.