This article explains how to set up a new usage based revenue account for allocating revenue by invoice. 

See How to update usage based revenue for how to update usage based revenue once set up.

To recognise revenue across a specific invoice based on usage or percent completion, go to Customers (top bar) > cog/settings (top right symbol)>Usage Based Recognition.  See screenshot below. 

To apply usage based rules,  set up the nominal account as a usage based account by using the button at the bottom of the pop-up screen.  

Then select each account you wish to add as a usage based account. 

To remove a usage based rule (that is, return the account to standard revenue recognition rules), use the bin at the right of the account rule.