dishwasher middle arm off..help??

Our newish dishwasher lost its middle arm, it just showed up one day in the rack when the dishes were pulled out…we have only had it since August and really want to fix it, but neither my son nor I can figure out how to reattach the $#^&*% thing! I am a bit worried we are missing a piece of the puzzle or something…anyone ever had this? can you walk me through it?? thanks!:smiley: