what theme are you using?
I’m using theme Twenty Twenty-Two.
Unfortunately this is part of WordPress’s mission to make WordPress totally unusable for new users, whilst experienced users will continue to use the myriad of already existing site builder plugins which do the job much better !!
If you want to continue to use the twentytwentytwo theme, the best I can suggest is that you work through this guide
How to Edit WordPress Sidebar in Twenty Twenty-two Theme?