How to set a spring between two placed particles

Activate the shift key, select one of the two particles with activated left button, move the mouse pointer to the second particles and release key and button.
Type of spring
The default setting for the simulation of springs are so-called Hook springs, ie springs that respond to pull and push provided that the distance between the relevant particles is smaller or larger than the neutral position. It is also possible to simulate springs which only respond to push (shock) or only to pull (rubber bands).
The setting of spring constant and rest length refers as default to all springs to be set.
The currently set spring constant, however, can also be applied to all existing springs by activating the corresponding button.
All other buttons are self-explanatory.

Damping Factor

A positive value for the damping factor means that all movements, caused by spring forces are damped.
The energy stored in springs is reduced by a certain percentage per computation cycle.
The movements caused by other forces are not affected.