If you download the deb file (my recommendation), you do not need the key at all. It is only needed, if you want to add the Oracle repository for VB to the software sources.
For completeness: Right click the link and select the command to safe the link as file.
Running Mint KDE 18.2 and problem with virtual with Windows 10
Forum rules
Before you post read how to get help. Topics in this forum are automatically closed 6 months after creation.
Before you post read how to get help. Topics in this forum are automatically closed 6 months after creation.