Well, this is disappointing. Lambda was my plan B if i didn't make it into the competitive program i selected.
Pick an easy language. I recommend Javascript or Python. There's a wealth of learning material and you can use these two languages to build a wide variety of things.
Pick something fun: a simple game, an interactive website, a blog, etc. Make it your objective, and instill in yourself a deep desire to make it. But don't get caught up on making it perfect.
Read a tutorial or two, experiment, and try to apply what you learned to the thing you want to build.
It'll take a lot of time. Whatever time you think it takes, multiply that figure by three. Don't stress out. You can't conceive of all the roadblocks or what you don't know.
If you get stuck, ask questions on Reddit, StackOverflow, Discord, etc. Learning how to ask questions builds your mental model of how this stuff fits together. Eventually you'll be able to answer a lot of your own questions.
Block out an entire weekend and go for it.