how do i install internet explorer onto Mac

You don't.

IE only runs on Windows. You would have to install Windows using Boot Camp or virtualization software such as VirtualBox, Parallels, or VMWare Fusion.

Many years ago, there was IE for Mac, but it was discontinued and is not compatible with modern versions of macOS.

Why do you think you need it? Microsoft is in the process of phasing it out, even on Windows.

You don't. In fact, you don't even install it on Windows as MS haven't made a version of it since 2013.

Why do you need it specifically?

As mentioned there is no Internet Explorer for Mac at this point.

Microsoft has however, made there new Edge browser available for Mac: https://www.microsoft.com/en-us/edge