Head back to the "hero" sprites, let's use a "when green flag clicked" block. Using code from the motion tab, position your hero that it always starts at the bottom middle of the screen. The coordinates for that would be: (0 , -150).
Grab a "key ____ pressed?" block as the condition for our If statement. Then add a "change x by 10" block from motion and switch it to -10 so we move left.
Now that we have left movement done, let's move right to Right! We can duplicate our work too, by right clicking on the If statement. and clicking duplicate. Then in the resulting statement, switch the condition to "right arrow" and the change to -10.