It’s usually as a % of revenue, e.g. “Working capital equivalent of 5% of revenue will be required at the beginning of each period.”
With that info, it’s straight forward: you calculate 5% of the CHANGE in revenue, whether positive or negative, and it goes in the beginning of the year, i.e. starting in the ‘year 0’ column. At the end of the project, this row should net off to zero.