The easiest way is to use pennies or flat washers to space out the spring coils before you take the spring off. This keeps the spring from collapsing when you move the kickstand to the up possition and it will just fall off. Mount new kick stand and move to down possition and remove spacers.
With the spring already off you should be able to flex or bend the spring sideways to open up a couple coils at a time on one side put spacers in and than flex it the other way to do the other side the more coils you put spacers between the longer the spring stays and you don't over stretch the spring
With the spring already off you should be able to flex or bend the spring sideways to open up a couple coils at a time on one side put spacers in and than flex it the other way to do the other side the more coils you put spacers between the longer the spring stays and you don't over stretch the spring