Going from memory, the referral links only really work when opened on a PC, and I think you need to use them to install Plarium Play.  In other words, opening one on a mobile device doesn't register properly.

That said, you can indeed use multiple accounts on a single device.  If it's a computer, then you can just toggle between the accounts through Plarium Play.  If it's a mobile device, you can log into each account through the account section in the top left corner.  Note that you can only be logged into one account at a time.  Additionally, each account can only be logged in once, so if you have both a mobile device and computer, you cannot log into the same account on each.

If you want to use multiple accounts at the same time on the same platform then you will need to use an mobile emulator like BlueStacks on the PC.  Most of the content creators use this and I think HellHades did a video on it.  I won't link it here as I'm not 100% sure if it's covered, but it should be easy enough to find.  Alternatively, you can just run 1 account on your mobile device, and a second account on your computer.