Ask HN: I'm a good programmer, I know nothing about marketing. Where do I start?

I'm working on a webapp for time management. (www.timeblocker.dev, if you're curious).

I keep procrastinating by tweaking technical things, but let's face it - there's no value to increasing the performance/maintainability of something that no one is using.

I know I need to market it, and I've made some posts here and there about it, but I feel like I have no idea what I'm doing.

Is there some sort of Marketing 101 youtube series or Coursera course that just covers some base level knowledge?