Change data in a CSV column

I have a CSV file that includes a column that is blank except for the header.  How do I set all the values in the column to a value that is the same for the whole column?

I have tried 

Import-CSV -Path "quota.csv" | ForEach-Object { $_.PURSE $_."1;0;0.00;2;2;15.00;3;0;0.00" }| Export-CSV -Path "output.csv" -NoTypeInformation

with no luck.