お客様各位 means dear customer. The first part,
お客様, means customer, or guest. That is easy to understand for me. But the meaning and usage of second part,
～各位 is not very clear to me.
Literally, 各位 is a respectful way to say "each" or "all". So "All customers" might be a more literal translation.
Practically, 各位 is often used as a suffix in formal headings to convey the meaning of "Dear ..." or "Attention all ...". These kinds of headings are often highly stylized and fixed, so don't let it concern you if the translation doesn't work on a literal level.