Whenever I send a link for my blog to someone it seems to pull through the web url as normal but it says underneath 'no title' and then pulls through a thumbnail image for a random image I've uploaded to my blog. Could possibly be the last image I uploaded.

How do I set this thumbnail image so its the same all the time (just my title and logo would be fine).

Gemini has given me mostly answers like use a plugin or CSS but neither are available to me whilst using the free version of Wordpress.

It did suggest uploading the logo image as a 'featured' image but that pulls it through full size into my home page and ruins all my formatting. So i really dont want it there. I'm tempted to create a random page and see if I can set the feature image there but surely there's a better way?