Have whatsapp account on a different phone?

I broke my last smart phone a while ago and since then I have been using a brick phone. About a week ago I bought a smart phone but it's not on my network so I'm just using it to play games and music on etc (with no sim card inserted at all) while still using the brick phone for calls, texts etc.

Upon trying to sign in to whatsapp, it sent a text to my brick phone. I went to the link provided but it gave me a pin code which I cannot see how to insert into the app.

Can I only use whatsapp if my sim is in that phone??

Thanks in advance.