Seems we are almost there! I hope.
[limo@lenovo ~]$ gpg --import rpm-public-key.asc
gpg: WARNING: unsafe permissions on homedir '/home/limo/.gnupg'
gpg: key FC918B335044912E: public key "Dropbox Automatic Signing Key <linux@dropbox.com>" imported
gpg: Total number processed: 1
gpg: imported: 1
[limo@lenovo ~]$