Arduino Boards
There are a multiple of Arduino and Arduino compatible boards. When uploading code to the board, the correct entry Board entry must be selected in the IDE Tools menu. For the Arduino boards that currently come with the ARDX kit, Arduino/Genuino Uno is the correct selection.
If the board you are using is not an Uno (or clone), and you can not locate it in the Board menu, you may need to install definitions for your board. Look at the Tools > Board > Board Manager screen. Your board may be in that list. If not the board should have come with some instructions for adding a board mangers URL to preferences. Adafruit has setup instructions for how to do that.
If none of that works, and google is not being helpful, it is time to start asking questions. The Arduino Forum is one place to do that. The issues page for our experimenter kit is another.
Before uploading a sketch to the Arduino Board connected to your computers USB port, the IDE needs to know where to find the board. This is done by setting port in the Tools > Ports menu. What the port name looks like varies between operating systems (Windows, MAX, Linux), and sometimes on which Arduino board is being used. The Arduino web site has a guide. It shows typical selections on a windows computer. The names will be different for MAC and Linux computers.