Welcome to the group.
Use resistors with common LEDs.
220 ohms should work in most Arduino situations.
If you don't, you will damage your Arduino.
Make sure you go through the 'Learning' tab at the top of this page.
Arduino links.
Watch these:
Some things to read:
https://learn.adafruit.com/category/learn-arduino
https://learn.sparkfun.com/tutorials/tags/arduino?page=all
https://learn.sparkfun.com/tutorials/what-is-an-arduino
http://playground.arduino.cc/Code/AvoidDelay
https://forum.arduino.cc/index.php?topic=384198.0
https://learn.sparkfun.com/tutorials/using-the-logic-level-converter
http://arduino-info.wikispaces.com/
https://learn.sparkfun.com/tutorials/how-to-read-a-schematic
.