How would I be able to verify the MD5 for a file that I downloaded on RPi?
In the terminal type
openssl md5 yourfilehere.
openssl output is incompatible with almost everything else and impossible to use to check anything except maybe a single file. the standard way to generate MD5 checksum is to use:
$ md5sum file1 file2 file3 sommorefilez* >files.md5
the result is saved to the file using the output redirect with
> sign and you may check the checksums later using:
$ md5sum -c files.md5
and just in case you'd prefer SHA checksums there are
sha256sum and so on...