The robotic arm kit is a fairly easy one to procure from eBay or Amazon. This is not very difficult to assemble and will require a few hours to prepare. Some of the robotic arm kits might not ship with servo motors, in which case, you may have to order it separately. I would say go for the kit that comes bundled with the servos, as there can be compatibility issues if you choose to order servos separately.
As you know, these servos will work using PWM and it's not hard to control them either. So, let's go straight onto it and see what we can do. Once you have assembled the robotic arm kit, connect the wires of the servos as follows:
Now, firstly, we need to know what are the maximum physical limits of every single servo connected on our robot. There are various techniques to do that. The very basic one is to measure it physically. This method can be good but you won't be able to ever utilize the full potential of the servo motor as you would be having some degree of error...