Navigate to "Financials" > "Data Management" in the left side menu. You'll then land on the "Accounting" tab.
If this is the first time you have uploaded accounting files, click on the "Upload accounting files" button.
Click or drag and drop the files in the box to upload. Save by clicking on the button "Upload accounting files".
If you already have uploaded accounting files and want to add more, click the "Upload accounting files" button.