To import a budget, you must use a file that you first exported through the software.
How to export the file
Go to Process → Budget Entry → (choose, current, next year, or next year +1)
Select the correct Budget Year for your purpose. Note: you may filter for only those accounts for which you would like to update the budget. Choose the Export button at the bottom of the screen. You may choose between entering a different budget amount per month or a budget for the whole year which will be divided evenly among the months.
You must save the exported file to your local drive so you can update it and then move on to the next phase, import.
How to import the file
Go to Process → Import Processes → Import Budget
You will then be asked to browse to the file and import.
What to do if your budget spreadsheet won't import
Make sure the file is in an ".xlsx" format.
For other trouble-shooting questions/answers see the linked articles below.