How do I see transaction history and credit usage?

Wow, it's really easy! You can see all the transaction history here:

1. Click the profile photo on the top left corner of the apps
2. Select 'Last Activity'
3. Create a transaction history in the 'Transaction' menu and create a credit usage history in the 'Usage' menu

And the by.U application can only show you the last 3 months of your transaction history