This is tricky because the key is actually to get te front tire as high as possible off the ground and then push forward on the handlebars to raise up the back tire.
First, try to do a stopie
Next, try and wheelie and as soon as you land your wheelie pop your back tire.
Then, try and pull up your back tire as fast as possible while you wheelie
You might get it.
Last, try and evenly pull up you back and front