Most legitimate businesses (those that always send from their real email address) comply with "CAN-SPAM" laws and provide a way to unsubscribe to their emailings. In most cases, these businesses will provide a link in their emails to remove yourself from their list. Going with this method reduces wasted bandwidth so that the sender no longer sends email to you at all (rather than just filling your quarantine with unwanted email).
If you are not sure you are dealing with an honest/legitimate business, or the unsubscribe method is unclear, you can add them to your Blocked Senders list. See: Blocking a sender's email address or domain. For this method to work, the sender must send from a consistent email address or domain.
If you can't block the sender because they're sending from random email addresses and you see a phrase in the messages that you know would never be seen in email you wish to receive, you can create a custom filter rule. To access this feature from the control panel, go to Settings > Custom Filter Rules.
If there are certain countries or regions in the world that you know you're not ever going to receive legitimate messages from (or that you can reasonably whitelist sender exceptions for), you can enable a geographic filter to block messages from those places. To access this feature from the control panel, go to Settings > more... > Geographic Filtering Policies.
You may also report a message as spam to our spam techs, and if there is consensus from other SpamHero users, new spam blocking rules will be created by SpamHero.