It all depends on which type of shock absorber you have fitted to your car. They look the same at first glance, but if you look closer at where the fescalised portion, (chrome bit) goes into the body of the shock, you may see if there is a threaded portion on the shock body. This will indicate that the shock can be taken apart.
To fit inserts, remove the shock absorber and unscrew the part that retains the piston. (Chrome bit) Take everything out and launch them. Then simply fit the insert, screw it all back together and refit shock. About 45 minutes per side.