The first step would be to identify and resolve the root cause of why your turbo failed initially, ensuring that the same issue does not damage your new turbocharger.
Secondly, replace your engine oil and oil filter to ensure clean, sufficient lubrication is supplied to both the engine and turbocharger.
The third step would be to clean or replace the oil feed and oil drain pipes to prevent any blockages that could lead to premature turbo failure.
Fourthly, clean the intake system, boost pipes, and intercooler to remove any excess oil or broken debris that may still be present.
The fifth step is to ensure that the exhaust system is not restricted and that the catalytic converter is still within specification. A blocked exhaust or faulty catalytic converter can create excessive back pressure, which may result in turbocharger failure.
The sixth step would be to fit the new turbocharger correctly.
Step seven would be to crank the vehicle without starting it in order to prime the oil system and allow oil to circulate through the turbocharger before initial startup.
The final step is to start the vehicle and allow it to idle without revving the engine. This ensures sufficient oil flow through the turbocharger while also allowing you to inspect the vehicle for any oil leaks.