All you want to do is pressurize the entire system to about 2-3 psi greater than you ever expect the system to operate with. The closer the crankshaft is to TDC, the closer one of the sets of valves in each cylinder is to being closed. This limits the amount of pressure lost during testing but it will still pressurize regardless of crank position. You want to use a large shop air compressor. You want to connect the boost leak tester to the turbos compressor inlet so every pressurized part of the system can be tested. If your PCV hose is bolted to your turbo inlet pipe, you will need to disconnect it and place a temporary block-off plate so you don't pressurize the crankcase. I usually remove the oil cap to minimize any crankcase pressure that may occur during a test.
Using a spray bottle filled with soapy water, spray every seal area from the turbo, intercooler piping clamps and hoses, intercooler, throttle body, intake manifold, boost solenoid hoses and anywhere else that's pressurized from the turbo. You want no leaks, which can be visibly found by the soapy water beginning to blow bubbles or create suds from the leaking air. You simply cannot be as thorough by sound or visual inspection alone. Also check that the PCV system is working and not allowing boost into the crankcase. I'm sure there are some good videos if you search on YouTube