This may be a very simple n stupid question but how do i use circuit tester. i saw some technitians use this , they tap it on the top of fuse n it lights up so i brought it. so how do i exactly use this... should the car be ON and i know that u crip that to postive terminal.... the wire from abttery to the device is short .... so if i wanna check the fuses that are IN the car, then where do i connect that hold on thing..