When I use my right hand indercator the fog light flashes as well and the rear light what can ido to repair the problem

When I use the right hand indicator the fog light and the rear light flash as well what can I do to fix the problem

Check all the lamp sockets on that circuit and check the bulbs themselves for broken but not burned filaments.
If the socket has broken tangs inside, replace it.
If a bulb is faulty, replace that bulb.
Thoroughly inspect the lighting harness to make certain that it isn't damaged somewhere.
Then let us know what you found.