problems with board

Projects General Guidance
1

I have bought a UNO R3 http://www.aliexpress.com/item/New-Avoidance-tracking-Motor-Smart-Robot-Car-Chassis-Kit-Speed-Encoder-Battery-Box-2WD-Ultrasonic-module/32361522385.html?spm=2114.01010208.3.2.Edyrno&ws_ab_test=searchweb201556_6%2Csearchweb201602_4_10036_10035_10034_507_10020_10001_10002_10017_10010_10005_10011_10006_10003_10021_10004_10022_10009_10008_10018_10019%2Csearchweb201603_9&btsid=0c874be1-fcb1-45d2-899e-f41ef54f5001
in this link and when i compile the code shows me this mesage that i have problems:Arduino: 1.6.8 (Mac OS X), Board: "Arduino/Genuino Uno"

Sketch uses 4,986 bytes (15%) of program storage space. Maximum is 32,256 bytes.
Global variables use 230 bytes (11%) of dynamic memory, leaving 1,818 bytes for local variables. Maximum is 2,048 bytes.
avrdude: ser_open(): can't open device "/dev/cu.usbmodemfd121": No such file or directory
ioctl("TIOCMGET"): Inappropriate ioctl for device
Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences. what can i do ?

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avrdude: ser_open(): can't open device "/dev/cu.usbmodemfd121":

That looks like you have not selected the correct serial port in the Arduino IDE before you tried to upload the program.

...R

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(deleted)

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Take a look HERE:
for some how-to