 Turn off the water supply and drain any remaining water from the pipes.  Remove the old basin if replacing it, by disconnecting the plumbing and unscrewing fixings.  Position the new basin, mark fixing points, and ensure it is level.  Install taps onto the basin and connect flexible water supply pipes.  Fit the waste and trap assembly, sealing joints with silicone to prevent leaks.  Secure the basin to the wall or countertop using appropriate fixings and wall plugs.  Connect the hot and cold water supply lines to the taps.  Turn the water supply back on and check for leaks in all connections.  Apply silicone sealant around the basin edges for a watertight finish.