When you say you can't find resources to design and build the arm, do you mean the whole project (for example, how to connect the Arduino to the servos, and how to program the Arduino to control the servos), or do you mean just the mechanical design of the robot arm (how to cut out something that will fasten to the servos to be the arm)?
If your question is the second, I can only sympathize that I have similar problems: doing simple mechanical design.
If your question is the first instead, I recommend you start with a little simpler project and work up to the robot arm. For example: project 1: get the Arduino board to blink an LED; project 2: build a circuit and write Arduino code to play a tone on a speaker (this will teach you the Pulse-Width Modulation (PWM) technique you'll need for the servos); project 3: build a circuit and write the code to wiggle two servos (this project lets you get everything working without having to think about mechanical design); project 4 - finally - mount the servos on wooden arms and program your new robot arm.