Our company is so disorganised that I do not even know where to start.
Do not start by trying to organise the entire company.
Choose one question: what have people asked you most often this week? Explain the answer in a two or three minute audio recording, upload it and turn it into your first document.
Then move on to the next recurring question.
You can rearrange the folder structure at any time, so you do not need to design the perfect system in advance. The best knowledge bases usually do not come from one huge documentation project. They grow from the real questions that appear in everyday work.
If you would prefer help creating the initial structure, you can also request consultancy or a complete implementation service.