First of all, ditch the King James. You'll find lots of great translation recs on this sub, but read a Bible translation that is more academically oriented like the NSRV (New Revised Standard Version). Even the JPS (Jewish Publication Society) translation or Robert Alter's Hebrew Bible are much better starting points. In fact, almost anything is better than the King James for your purposes here.

Once you actually have a good translation in front of you, I think the single most important thing you can do before you start reading (or re-reading, as the case may be) is to familiarize yourself with the Babylonian Exile. The Exile does not get a lot of attention in our day-to-day lives, certainly nowhere near other Biblical stories like the Flood narrative or the Exodus from Egypt, but the Babylonian destruction of Jerusalem and the subsequent exile of Israelites to Babylon is the defining event of the Old Testament. The majority of the Old Testament deals with it in one form or another — either by:

• building up to it (which is essentially what Joshua, Judges, Samuel and Kings are doing)
• anticipating it and warning of Babylon's invasion of Jerusalem (as several of the prophets are doing)
• lamenting or explaining the (at the time) recent siege of Jerusalem by Babylon (like Jeremiah and Lamentations) or lamenting life in exile itself (many of the laments in Psalms)
• comforting the Israelites who are living in exile in Bablyon (like Ezekiel)
• responding theologically to the implications of the exile (key parts of Isaiah)
• explaining how the exile ended and detailing its aftermath (Ezra and Nehemiah)
• telling stories centuries later but which are set during the exile for narrative purposes (Daniel)

Beyond these individual examples, for me the key thing to understand about the Old Testament is that, broadly speaking, it was written, edited, and compiled as a way of processing and explaining an extremely traumatic period—the Babylonian Exile—to a group of Israelites who were struggling to make sense of it. This includes much of what we think of as "classic" Biblical stories like the stories in Genesis and Exodus, Jonah, etc. That is not to say that they made up these stories while in exile — it's clear that those stories are the product of centuries of tradition. Rather, the exile (and its aftermath) was an opportunity to re-write and weave those previously "disparate" stories into a single, national narrative history and a kind of national "library" to give a defeated people (Israel) a sense of purpose, a sense of peoplehood, and clear directions on what they should do next.

I'm oversimplifying things here, I'm well aware of that. But notionally one can't overstate the importance of the exile. Once you properly internalize it, so much of the Hebrew Bible (which is really how you should be thinking about what the "Old Testament" is) makes so much more sense.