Budgeted Voyages can be located from the tab in the Budgets module.

At the top of the list with budgeted voyages, if you have the required permission (Voyage Contributor Role), a "Bulk Update" button is available:

Clicking the button will change the list to be selectable, where the desired voyages can be selected for bulk updating. After selecting, press the update button below the filters to open a modal with available fields to bulk update: