I recently went to the new quickbooks online. How do I create a billing statement of open items to send to my customers like I used to do easily before?

From the Homepage screen

Click “+” sign (top middle)
Select “Statement” under Other header

How to email statement to a customer?

Select “Edit” under Delivery Method column
Default could be “None” 
Select “Email” from the pop up screen and follow the instructions
Select “Create/Send Selected Statements” button
It will send email and will end with “Statements Created” message report.