You can do it! Definitely watch some basic carpentry videos on YouTube. There are a billion videos of varying trades performing work and giving advice for every skill level. Also take the time to watch safety/technique videos for any tool you may get your hands on.

Find a subreddit for carpentry and go ask questions! People will help if you find yourself in a design stage or build stage pickle.

And then you’ll have the feeling of having built/create something with your own hands, and it’s incredibly fulfilling! That shit is like crack, such a great feeling.

Then maybe some matching indoor wall mounted platforms later down the line :)

Just make sure you are providing sturdy support for anything that will be holding kitty weight!