It is very easy to attach armrests. For the Comfort Move: slide the metal end piece in the sleeves under the seat, and tighten with the knob. For all other models: a connection piece needs to be installed to the mechanism of your chair (when ordered with armrests we have that already done for you in the factory). Then, slide the metal end piece in the connector-sleeve under the seat, and tighten with the knob.