A Bias Tee provides the power to the LNA. The RTL-SDR v3 has one built in so an external one is not required.
So it would go... RTLSDRV3 > LNA > Antenna.
This was my exact setup up until last week when my 1 week old RTL-SDR v3 bit the dust. Back on the FA Prostick Plus while awaiting a replacement
To be more precise: Bias-Tee provides the power via the coax to the LNA. So it could look like this:
USB-dongle > Coax > LNA > Adapter/Pig tail > Antenna
That was my exact setup, too, but Bias-T was not reliable with the RTL-SDR V3, causing performance to drop significantly. While testing the Triple Filter LNA went to heaven, now I'm waiting for a replacement.
When the RTL-SDR V3 dongle loses its power, Bias-Tee is turned off. Just to be sure, I also bought a NooElec NESDR SMArtee, which has Bias-Tee always on (hardware).
Modified it slightly by sticking a few heat sinks on the casing to keep it cooler. In the meantime, the FA Prostick Plus is also back on duty.