The best way to start is by painting a base coat that will be your brick mortar color. That's the lines between the bricks. Next you will tape off your brick pattern. Using 3/4 inch blue tape, you'll line off what will end up being your mortar lines.
After you've taped off the wall, you can paint the main color of your brick over the wall and the taped mortar lines. Usually if your brick sample is primarily red, this is the color you'll paint solid first.
Next, if you are using other colors to create more realism, you can mix your other colors individually in glaze.
I have found that a sponge is the best tool to apply the additional colors. A tip for applying additional colors is that I try to build up the colors from the most to the least.
For example, if the brick is mainly red, that is the solid base. If you see more black or brown as the next primary color, that should go on next using the sponge to allow plenty of red to show through. Then let's say you notice a little white or yellow, just apply a little of this glaze with your sponge just as a highlight.