So I guess before you had successfully installed your twin turbo you have bought the following
auto parts:
*intercooler and piping kit
*blowoff valve
*turbocharger manifold
First thing to do is to change the twin turbocharger manifold into a single turbo manifold.
After that, Use a single turbocharger intake and connect it to the inlet. Take the other side of the intercooler and attach the remaining hoses and pipes and connect those set of pipes and connect them to the engine's air intake system.
Always double check what you do. After that fill your car with new oil and you're done.