help with 3rd register of the clarinet?

This is normal for people new to this register, also called the Altissimo register. Those two notes are very commonly difficult to play (E is a tough one for me, or it used to be, it was always sharp).

The best way to get used to these notes is long tones. Just play the notes in the altissimo for long periods. Pick one, say E for example and play it at Forte for as long as you can, with as much control as you can (not letting the pitch drop or waiver, I'll go over that next). Then play that same note at piano, this will be harder to keep in tune etc, but if you keep working at it, it will improve, I promise. Try playing as beautifully as you can. Repeat on any other notes in the altissimo.

Also, when practicing these long tones, use a tuner. You may see that your pitch is wavering ever so slightly or in greater amounts. Either way, think fast cold air, and steady. When I "think steady", I think about nothing in my throat or mouth moving at all. My air stream is focused (I'll go over that next). If you are flat, think EEEE in your throat and mouth to raise the pitch. If you are sharp, open up in your throat and think AHH. I like to think about singing when I am sharp because I used to take vocal lessons. Big open spaces. But the amount of space in your mouth / throat will vary depending on how sparp / flat you are.

To practice focusing your air, use breathing exercises. Start with your hand close to your face, and blow with good air pressure for 8 counts. Do this a couple of times. When you feel that your air is focused (not moving around your hand, but only hitting one area), move your hand further away from your face. Repeat. This probably won't be perfected the first day, so keep at it.

The more you play in the Altissimo register, the better you will sound. Keep practicing long tones.

Practicing your scales up in that range will also help.

Also, make sure your embouchure is not pinched. Keep your chin pointed down etc.

Best of Luck!!!!

Make your mouth is adjusted right on the mouthpiece and your reed is moist and make sure the holes are all covered for the note your palying