Format an SD card to Fat32 and copy the included bin file to the card root. The default EZ Client can be found in the device files on the server however installing EZFlashTools.exe will give you access to the client with additional tools.
“When you get the card you first need to place the ezfla_up.bin on the root of your Fat32 micro sd card. Something that was not clearly explained on the site but easily figured out. You will also need to put the rom on the SD card but NO drag and drop here you need to patch the roms first with the EZ4Client. However, I found a better all around choice: the EZ-Flash IV AIO by MartinAugustsson on GBATemp. It is a very useful program for doing this and much more.
Now, from within the EZ-Flash IV AIO on your PC, click the EZ4 Client button. From here you will see the window for “EZ-Flash IV All-in-one” pop up. If it doesn’t find your SD card it will ask you what drive the SD card is in, select it and you should see ezfla_up.bin and not much else. Click open, find your GBA games and pick one. Now just hit send and it will be on your SD card. Take your SD card and place it in the EZ Flash IV and place it in your system.
When you boot for the first time you will need to be holding the right trigger to load the firmware (ezfla_up.bin) onto the EZ Flash IV you will then be greeted with a loading screen.”