How to add Ultrasonic Sensor to the board?
1) Not really. You have so little space and you have to selder them. Try using wires

2) If you want it to be flexible use a sandard solderless breadoard on the center of the car and then with male-female jumperwires try connecting them. 

3) The board has traces. That means some holes have a very specific purpose.

Updated:

On every breadboard the holes are connected verticaly. For example, in the image from your breadboard you posted 1A, 1B, 1C, 1D and 1E are connected together.
If you would like to have all of the 3 sensors better use wires and then atach them on to your breadboard.

Here is a picture: 
https://www.dropbox.com/s/3ij4w6eytio8p08/Screen%2016-25-31.png?dl=0