An archive notebook becomes easier to use when it begins with a manageable question. A broad interest in the past can lead in many directions at once. One named place, a particular object or a short period provides a more practical starting point.
Write the question at the top of the page and list what you already know beneath it. Keep that list separate from assumptions and stories you have heard. A promising possibility can guide a search without being treated as a settled answer.
For every item consulted, leave enough information to find it again. Add a short description of what it contributes and what it cannot tell you. The note should make sense to your future self without depending on a memory of the research session.
End with a revised question rather than a forced conclusion. A useful first session may reveal that the original question was too large or that a different source is needed. That clarification is progress worth recording in its own right.