Note that the breakout has pins on two sides. Be sure to use the side with the UART pins. They are labeled TXO and RXI. We'll demonstrate using SoftwareSerial on the Metro 328. Here's the wiring:
See the Arduino I2C Usage section for details about installing the Adafruit GPS Library. The same library is used for UART.
We can test basic functionality using one of the examples from the library. This won't do any parsing. It simply dumps the raw data sentences as received from the GPS module.
Open up File -> Examples -> Adafruit GPS Library -> GPS_SoftwareSerial_EchoTest and upload to your Arduino board with the GPS module connected.
Once the sketch is uploaded, open up the Serial Monitor (Tools -> Serial Monitor) at 115200 baud. You should see something like this:
If you see this, then you are successfully talking to the GPS module. Once it obtains a lock on the GPS satellites, which can takes several minutes, there will be more information in the sentences. To see that information in a more user friendly format, try running the GPS_SoftwareSerial_Parsing example from the library.
The above example demonstrated UART usage via SoftwareSerial. If you have a board with an available hardware UART, you can use that also. Simply connect to the TX/RX pins for the hardware UART for your particular board and then see the examples in the Adafruit GPS Library with HardwareSerial in the name.