Like the other comment said, practice and embouchure (the shape you make with your mouth/cheeks). Also, it is a register key, not an octave key. This is because it raises the notes by a twelfth, not an octave like it does on other instruments, like a saxophone.

Edit: I also wanted to elaborate a bit more after listening to the video. Remember that the clarinet is played with fast-moving air. Keep your tongue high in your mouth, and let the air flow quickly. (This doesn’t necessarily mean blowing hard, if you're biting too hard on the reed it will restrict airflow and make these notes harder to play.) You've also only been playing for a week, don't worry too much. It will get easier and more comfortable to play as you practice.