The handset is your controller for raising/lowering your desk. It can be positioned anywhere on the underneath of the desktop but is best positioned at the front edge for easier access. If you have your desktop inserted or pre-drilled, you can choose to have it on the far right- or left-hand side. If you are assembling the desk without pre-drilling or inserts you can position it wherever suits you best.
If buying a manual desk the handset location is where the handle is.