The first one would be to resolve the issue as to why your turbo failed initially so that there is no failure to your new turbocharger. Second step would be replacing your oil and oil filter so that there is clean and sufficient oil running through your motor and turbocharger. Thirdly I would say, clean or replace your oil feed pipe or your oil drain pipes to prevent any blockages and premature failure from happening.
Forth step would be to clean your intake, boost pipes and your intercooler so that there is no unnecessary oil or broken pieces inside. The fifth step is to make sure your exhaust is not blocked and the catalytic converter is still in spec otherwise it is going to create back pressure that is going to lead to the failure of your turbo. Sixth step would be to fit your turbocharger.
Step seven I would recommend swinging your vehicle without starting it just to get your oil lines primed and your turbo blend. Number eight would be to start your vehicle and not rev it, let it idle so that there is sufficient oil running through and inspect your vehicle for any oil leaks.