Publisher is one of the programs of the Microsoft Office suite that is not available in for Mac, meaning that it is not possible to download this software if you use an Apple computer. Along with Access, Microsoft does not offer these two programs on this platform, regardless of the subscription plan you may have. Publisher allows you to lay out all kinds of documents but you will have to look for an alternative solution, and there are several. They are a little bit more difficult to use them but they could be your only solution if you want to work with this program.
The first alternative solution is Bootcamp, a tool included in the Mac operating system that allows you to have a partition with the Windows operating system installed on your computer. In this way, you just have to restart the computer and use Bootcamp and Windows to work with your copy of Publisher. In order to use it, you will need a Windows system image that can be used by Bootcamp and then log in normally with your Microsoft account to install Office and Publisher.
Your second alternative solution is to download the Publisher EXE and install it on your Mac using a virtual machine, such as Parallels Desktop or VMWare. These programs are able to virtualize Windows, that is, to see on the screen of your computer a good old Windows with the same functions, allowing you also to install the Office EXE and use the Publisher available on that operating system. You just have to perform the installation of the software as usual.