Uploading Error

I am trying to upload code to my watch that I made from Adafruit's kit. I get the following error:

Arduino: 1.8.5 (Linux), Board: "LilyPad Arduino, ATmega328P"

Sketch uses 24134 bytes (78%) of program storage space. Maximum is 30720 bytes.
Global variables use 1416 bytes (69%) of dynamic memory, leaving 632 bytes for local variables. Maximum is 2048 bytes.
avrdude: ser_open(): can't open device "/dev/ttyUSB0": Permission denied
An error occurred while uploading the sketch

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

Will someone please help me? I am also getting a similiar message when trying to upload code to an Arduino 101.

The key error information is this:

avrdude: ser_open(): can't open device "/dev/ttyUSB0": Permission denied

For some reason, you do not have permission to use serial port ttyUSB0. This is a Linux issue that you will have to take up with the user community for your unspecified brand of Linux. It is not an Arduino problem exactly.

This normally indicates that your user is not a member of the dialout group, you need to add your user to this group to access serial ports.

Googling for "serial port permission denied linux" generates a lot of hits, with people debating what steps are needed to fix it - different distros require different steps...