I am a beginner and want to start with the Teensy, share the tools and tutorials which I should start from absolute zero? let me introduce you, I am an Electronics hobbyists who loves to play with new gadgets.
Assuming you have a Teensy and the Arduino IDE installed....
Go to the File menu and look for examples, see 01.Basics and find Blink, it should be your first. Try other ones unit you can write your own program to measure a small voltage, then learn how to write to an LCD, SD card. Go from there.
I find it easiest to start if I have a project in mine.