Unless she has a really fat ass, you should be able to get balls deep into her cunt quite easily.

She needs to be on her knees, legs spread a bit and leaning back. She needs her head down so her tits are against the same surface as her knees. this will line her cunt up for the best angle to get cock into her. You should be able to see into her cunt. Then you have to get your cock at the same height as her cunt. You may need to be standing up behind her at the edge of the bed, or kneeling on a pillow to get your cock and her cunt at the same level.

Then you just stick your cock into her open cunt and fuck. Your balls should be against her cunt when you slam into her. It is acceptable to grab her hips with your hands for added leverage.

The angle of the dangle should be perpendicular to the pelvis
--------------------------------------- added after 2 minutes

If that doesn't work ask for a blow job.

I have a theodolite you can borrow....
if that doesnt work, ill let you practise on me.....xx