The Arm Cuffs are plugins, i.e. add-ons, and they require the core cuffs (Wrists + Ankles) to work.

To activate them, you need to first make sure you have the core cuffs set up in your HUD (HUD comes with the core cuffs).

Then, just wear the Arm Cuff activators that came in the box. That will take you through setup which gives you the cuffs.

Sometimes, it will say no cuffs detected. Make sure the arm/thigh cuffs are the same type (i.e. leather or steel) as your core cuffs.

If you're sure they are the same type, then just reset the HUD by saying "/1.reset" or by clicking the LULU logo on the HUD > HUD Menu > HELP... > reset.

If you need someone to walk you through, you can also ask people in https:lu2.me/group - especially the Fashionistas.