Recreating Classic Electronics Kits
Contributors:
Nick Poole
Nick Poole 
Add Spring Connectors
The first thing to go in will be the spring connectors. These can be kind of a pain, but one trick that I learned to make the whole thing easier is to use a pair of pliers to bend the end of the spring out. This gives you something to stick through the hole and gets the spring started. Once in, simply give it a few twists so that it screws its way into the cardboard. This is made less painful by grabbing the "wall" of the spring with a pair of needle nose pliers and twisting that way. Your hand is still gonna hurt after about 20 of them, though, so don't be afraid to take a break.
Bending the spring makes it easier to insert into the board
Once all of your springs are in place, you should have something that looks like the picture below!
Springs are in place but it's still missing something...