$ gpg --recv-key 0xBE86EBB415104FDF
$ gpg --fingerprint 0xBE86EBB415104FDF

...check it matches fingerprint above...
$ gpg --verify SIGNATURE-FILE  SOURCE-FILE

also, more common:
verify a signateure: sha256sum -b yourfile.iso

---------------

Verify a file signature:

	gpg --keyserver-options auto-key-retrieve --verify linux-5.12.7.tar.sign

Check the signed hash of a file:

	gpg --verify SHA256SUMS.gpg SHA256SUMS

Same:

	gpg --keyserver pool.sks-keyservers.net --recv-keys 74F12602B6F1C4E913FAA37AD3A89613643B6201
	gpg --verify SHASUMS256.txt.asc