I asked a similar question some time ago about the LED's and I believe the same answer will apply to the switches.
The only way is to delicately solder into the components connection on the circuit board.
If your eyes are better than mine, then you'll probably have no trouble.. !
I have already done some testing on the LED's, there is very little current available to drive larger LED's unless you use it on a switching transistor or something.
I expect S1 and S2 would be easier as it could be directly connected to a switch.