Set Focus is similar to the Window Activate command, but uses a control instead. It brings the window that contains the selected control to the front and then sets focus to the control. This is most useful for edit box controls. Set focus to the edit box and then use the Text Type command to insert text, etc.
Script Editor > Expand Window Controls Category > Set Focus
Set Focus to Control
First use the Get Control or Capture Control command to save the control to a variable. Then select the variable to receive focus.