First, I get it and if I could snap my fingers and make your arm fat disappear I would only charge u $1000 and u and all your friends would pay it.
However, there is no secret trick. No special workouts, no super secret set of workouts, to tighten your arms.
You can not choose where your body loses fat. Unless u use a vacuum and suck it out.
Notice how all the girls with tight arms also have tight waists, thighs, and legs?
Fat loss overall makes u have toned arms and legs.
So so instead of looking for tricks to tighten your arms start making changes that will help u lose weight.