Ready, Set, Boot!
I recommend backing up the two files we just created, ssh and wpa_supplicant.conf, to your hard drive in case you need to reset to Pi from a fresh image.
Now, we are ready to eject the microSD card. Depending on your operating system, you can probably right-click on the drive to select eject or there is an eject icon next to the drive. Safely ejecting is good practice as that will ensure there are no processes that are writing on the drive. If you eject while the card is being written on, you end up with corrupt data.
Plug in your Ethernet cable now, if you are not using Wi-Fi.
Always insert your microSD card into the Pi before connect the power cable and if you were to take the microSD out, make sure to power off the Pi from SSH first.
Before going to the next step, make sure your Pi successfully powers on. There should be at least one LED on the board that would be flashing or on steady.