If you have Programming Massively Parallel Processors: A Hands-on Approach, 2nd Ed, by David Kirk and Wen-mei Hwu (Morgan Kaufmann Publishers (2012)), read Chapter 1 and 3.
Alternatively, Edition 1 is available on-line in draft form. Here is Chapter 1 which roughly corresponds to Chapter 1 of Ed. 2. From this point on, the edition deviate; Edition 2 gives a gentler treatment of CUDA and device material than Ed. 1. Roughly speaking, Chapter 2 and Chapter 3 from Ed. 1 are equivalent to Ed. 2’s Chapter 3, but primarily use the Matrix multiplication example. Ed. 2 introduces the material a step at a time, culminating in Matrix Multiplication.