[Update] There is now a short guide in the sheet, detailing many of formulas, entry points, etc.
What do I need to edit?
All that needs to be edited are the light green cells in each tab. The spreadsheet will do the rest of the work.
Each month, simply enter your spending per category and any investment updates.
On the "NW" (Net Worth) tab, indicate the first month of data you plan to enter. The rest of the dates will populate themselves.