Open the Excel file
Go to File
Click Info
Select Protect Workbook
Click Encrypt with Password
Delete the password from the box
Click OK
Save the workbook
Open the protected worksheet or workbook
Go to Review
Click Unprotect Sheet or Unprotect Workbook
Enter the password
Save the file
If the file is protected by a password to open, enter the password first
Then remove the password using Encrypt with Password as above
Save the file
If you do not know the password, use the original unprotected file or request access from the file owner