Setting up email clients to communicate with VPOP3 is straightforward. VPOP3 is a POP3/SMTP (and IMAP4 if you have VPOP3 Enterprise) email server, just like an ISP's mail server, so you set up the email client just as you would for any other email service, but using the VPOP3 server address as the incoming & outgoing mail server, and using the username & password defined in VPOP3 as the login details.
There are very many email clients available, so we can't give step-by-step instructions for all of them, but some are given below. For other email clients just use the basic concept above. The email client documentation should be able to help with the specifics of where you enter the relevant details.
When setting up the email client, you need to know the IP address of the VPOP3 server. See the Finding the VPOP3 IP Address topic for how to do that.