You only want the main character to move up if you press the up arrow key. To help write the sentence, "If I press the up arrow key, then my character moves up" grab the "if-statement" block from inside the orange "control" blocks.
If-statements only work if they have a condition that tells them when to run. When do you want your character to move up? Only if the player presses the up arrow key! This block can be found in the light blue "sensing" section.
Right now, this code is only checking if you're pressing the up-arrow at the start of the game. But you want to check if the player is pressing the up-arrow key for the whole game! This block is found in the orange "control" section.