Yep. You have to fit the derailleur down the dropout a bit - the odd nut goes on the inside of the frame and sits at the back of the droput and the ‘C’ shape of the derailleur mount should align with the dropout.
I have one on a shopper bike I am modifying and truth be told I ditched the bolt and nut and just use the axle nut to hold it in place. I have considered drilling and tapping a hole in the dropout to accept the little bolt but for now it’s “loose” fitted.