I think KVZ’s instructions are good.
What makes OKRs work, and where I thought the Doerr book was good at explaining theme, is how each KR is linked to an objective of someone else, usually a subordinate individual or group, sometimes a peer with a different job function.
Since OKR is a simple idea, it’s transmittable enough that an organization can use it to link itself together so that specific direction from the top drives down to the bottom of the organization rapidly, which lets everyone drives toward completion high level goals in the way that’s appropriate to their job description.
For personal/solo use, there’s some value in OKR methodology to forcing yourself to write quantifiable sub tasks. Since it’s all you, though, you might as well go beyond KRs and write out the whole project outline for yourself in the same document or tool.