to remove the stock units, they come off the bike as an assembly. Remove the screw on the end where the rubber stalk meets the frame rail...then twist to "unlock" the stalk and it should pull out as a whole with wires attached. The connections are under the seat, so disconnect them before removing the stalks.
This is what it looks like when removed. Take note of the rectangular end that fits and lock into the frame rail when inserted and twisted.
The rear blinkers are 2 wire, the front ones are 3 wire and have a running light circuit that the rear ones do not have from the factory.
If you are buying another type, you may have to modify a bit to make them stay put (threaded ends are not factory type)