There are two way to connect a GPS to a raspberry pi. One is through the GPIO header pins and the other is through the USB port.
The GPIO way can be complicated and FlightAware is not able to support this. You need to know the pinout for the GPIO and then how to physically hook up the GPS and then finally to install the drivers to use those pins. There is also no easy way to troubleshoot any wiring problems. Connect a wire to the wrong GPIO and it will not work.
The USB GPS dongles are much more plug and play. This is the preferred method for most people. Also, FlightAware will not support setup of the GPS module but we can troubleshoot problems with GPSd and PiAware not working together.
TLDR: Definitely go with the “USB GPS receiver” setup. Amazon and eBay and whatever online store has them fairly cheap
There are youtube videos with step by step instructions.
Look up “stratux GPS setup” on youtube.
or google for “stratux GPS setup instructions”