How do I arrange these logs?

There is no exact order you have to follow when arranging your logs in the fireplace. A couple pointers may be to place the larger logs on the bottom to create a sturdy foundation. Leave a little room, say 2 inches, between the logs to allow the flame to make it's way through. Be sure to not block the gas flow, if you do you will need to rearrange. Once the base is sturdy continue to build upward until you get a look that looks right for you and your home.