New Mac Desktop, Lightroom Catalog not showing

Hello!

I recently got a new iMac and was trying to get into Lightroom to edit photos. When trying to open Lightroom, it says that my catalog cannot be found. How can open Lighroom to edit photos on my new computer? I am also curious how I can work on the same catalog on two different devices. I will still use my laptop when I travel and will need access to my catalog from there as well.

Thank you in advance!