When you download the distro you want off the website, just make sure to grab the asc file and signature. Its the same as verifying for example coldcard software, or new version of sparrow
Discussion
Gpg --verify ascfilename.asc
Do I put this into terminal?
Yes that's right. I couldn't find the asc file either but I did find this way to verify Ubuntu. https://ubuntu.com/tutorials/how-to-verify-ubuntu#1-overview
I can't find an asc file or signature for ubunutu