Hi and welcome to PSG
First thing you need to do is extend the canvas, go to Image and Canvas Size
Then make a selection with the rectangle marquee tool
Hit CTRL + J to copy that to a new layer and then hit Shift + Backspace to open the fill dialog
Select color and choose the color of choice, then CTRL + T on that layer to enter free transform
Right click and select perspective
Then drag the lower left corner handle to the right until you get this
Result
You can then CTRL + J that layer to copy it and again hit CTRL + T on the copied layer and then right click and select flip vertical and hold the shift key and move it to the lower part of the image
Final result