You can set charge-out rates in your rate cards (Under Manage>Rates) and then change the unit on your project budget as well.
Click on Manage> Rates.
For Rates- and then on Details for the specific rate card- you can then set it to Daily rate.
3. Change the it on Project budgets if needed as well. Click on Projects and then on Details on the specific project.
4. Click on Budget and make the changes in the window.