sparkfun openlog n00b question

I have had pretty good success using most kinds of breakout cards and sensors in my arduino projects so far, but I am stumped by my first attempt at setting up data logging. I bought a SparkFun OpenLog card because it claimed to be "simple" -- and now am quite confused about how to connect it to my Uno or Leonardo. I didn't realise at first that it was an independent ATmega rather than a peripheral, and that it has to be connected to a data source via a serial port. The documentation seems to say I should connect it to the "Serial" pins D0 and D1 on my Uno/Leo... but I thought those were dedicated to USB.

If they are dedicated to USB, then wouldn't the OpenLog device conflict with USB communication -- and if it did conflict, how could I edit and upload my sketch as I try to test the OpenLog device? I must be missing something very obvious...

Is there a way to set up a second serial interface -- other than the USB connection to the IDE host -- and attach the OpenLog to it? I feel a little embarrassed asking what sounds even to me like a stupid question, and yet an hour or so of googling has not yet clarified this for me.

[update a few minutes after posting: at last I seem to have typed in the correct search terms and found this:

am I on the right track? can I connect an OpenLog to two selected digital pins and use this library to send data to it?]

can I connect an OpenLog to two selected digital pins and use this library to send data to it?

If the OpenLog hardware supports such an option, yes. If you can't tell, post a link to the device.

Hookup Guide

published by the mfr. it has an "FTDI header" (new concept to me) intended to plug directly into a mini Arduino board, but I don't have a mini Arduino board; I want to use one of my collection of Leonardos... I'm thinking, based on the "how to have more than 1 serial port" link above, that I can wire it to any digital pins configured to be a serial port.

but before I blow something up thought I'd ask if I'm heading in the right direction.

The Leonardo has 2 serial ports - Serial, which is not connected to any pins, and Serial1 which is connected to pins 0 and 1.

Connect your device to pins 0 and 1, and use Serial1 to read from/write to it.

On an UNO you can use SoftwareSerial on any pair of pins except 0 and 1. That's a poor solution though. Stick with the Leonardo and use pins 0 and 1. Address this as Serial1 in your program.

Power for the OpenLog should come from a convenient Arduino power pin. I think it runs on either 5V or 3.3V. (I don't remember.) Ground should be connected too.