You can’t teach yourself karate, just like you can’t teach yourself wrestling. And that goes double for an art like jujitsu, judo, or aikido, for example which are more partner-oriented than karate.
What you can do on your own is practice striking something like a makewara or hanging bag or whatever, and train your flexibility and strength.
Trust me on this, you will absolutely need someone who knows something about martial arts to show you all the stuff that goes on “behind the scenes”, so to speak, that you can’t see in pictures or read on a page.
Besides, it’s more fun with other people. There’s a good reason right there to find a decent school somewhere.