Couldn't be simpler.
The ONLY places that you are allowed to enter anything will be the cells colored GREEN.
All other colors are distractions! Well ok, they do make the spreadsheet look better.
Within the sheet, you can typically navigate within the GREEN cells using merely the Tab key on your keyboard. Of course, arrow keys and mouse clicking works too.
You should start with the sheet tab named "NEXT BEST BUY". This is where you enter the number of properties that you have already own in your Mob Wars game.
There will be a Green colored "<<-Here" indicator in a column heading "Next Best Buy" that will move up and down as you enter your properties. The spreadsheet is calculating on-the-fly as you key in stuff. Only pay attention to it AFTER you have keyed in everything that you own. Only then will the indicator make sense. For newbies, your best bet is to follow the "Next Best Buy" Indicator for your next purchase. Buy what you can afford in the Mob Wars game, then flip back to the spreadsheet to update your purchase. The Indicator will then point to the next recommended purchase. Yes, you will be prompted to buy a lot of Villas and Restaurants..
Update your current Stockpile in the Stockpile sheet tab too - this will allow the calculator to correctly work out your net passive income. You will be able to cross-check these values within your Mob Wars game at the City Menu.
Check out the Analysis sheet tab to see how much time is needed to save for your desired next purchase. Strategies in a different post.
Save your spreadsheet.