The way you phrased your question is that I interpret it as not “how do I generally manage any kind of data” (because, really, not just historians have this problem), but rather how to make sense of “historical data” (so, let’s say, information about events, people, and other particulars of the past).

The answer of a historian would be: questions.

What we call “questions,” in the broadest sense, is just “topics.”

You may be aware that historians very rarely are content with merely asking “what happened?”: rather, they show what happened in a certain kind of context (philosophically, we'd call these aspects). In other words, the “what” is imbued with a certain kind of meaning (or sense, if we want to distinguish like philosophers - or Germans like me - do).

Thus, if you want to make sense of your disparate information, then, perhaps, start organizing it in this way: what kind of things do you care about? The obvious "historical" things may be certain persons (important for biography), or important events (again, important). But then, think of more general concepts like: kinship, gender, power, social status, arts, science, knowledge, religion, warfare, agriculture, etc. This list is potentially endless, but this becomes quite relevant to what we usually talk about: what can the life of X tell us about concept Y? (But then, what can concept Y tell us about the life of X? is equally valid!)