Make sure your A/T switch is ON, use the "TO/GA" button on the Thrust Management Panel (Modes 1 or 2 as additional options) - notice mode is selected on the upper EICAS and "TO" shows in green on the PFD

Push throttles up to 40-50% and hit the THRUST button.  PFD "TO" changes to a green box around it and throttles advance to required thrust