I want my Arduino UNO to read data from a .txt file

+1 for the serial input basics tutorial.

If you use the Robin2's tutorial, the text will be in the form of a string (null terminated character array) so you would use the string search and compare functions to find matches that could actuate the LED or, later, the motor.

If you want more help, post your best attempt at the code, a description of what the code actually does and how that differs from what you want.