If you are inside Openledger wallet and choose from the right window of assets groups OPEN.BTC you have the list with all BTC assets of Openledger down the line.
On the right next there is a search field where you can use "USD" as a search word.
You get two assets down the list one is USD and the other is Open.USD .
USD is BitUSD . Thats what you are looking for.
I had the same problem also.
I think i helped you with this.