Use and modify.
The business plan asks the same questions that investors will ask themselves, in an order that makes narrative sense. No-one will read the business plan, but it helps you specify the thoughts, define the assumptions, and gather the data that you will need in your pitch and elsewhere. The articles in the Plan section of this website tell you how to answer these questions.
The excel files have inputs (assumptions) in red- you should change these to reflect the actual numbers that reflect your business conditions. They are hard coded. Anything in black is soft coded, meaning it is a calculation made using the hard coded data as inputs. The excel files begin with an Assumptions page, which is mostly in red, and then the useful outputs are all on the subsequent pages, in black.
N.B. every assumption needs to be backed up somewhere with as much data as possible, in the business plan, data room, and pitch. Investors will dig deepest into the assumptions.