What "installer"?

I want to install the thunder overlay map and example set, to use with bitwig on windows. I’ve downloaded “Sensel_Morph_Bitwig_WithScripts.pkg” but i have no idea how to install, both the morph user guide and the youtube tutorial, say to just download the .pkg file and djust use the installer. What installer would that be? Am I supposed to just know this? I’m so frustrated I could scream.
I’ve searched everywhere I can think to search – to no avail.
Can anyone help me?

After downloading when you click the file that you have downloaded a command will appear and you have to follow them as instructed. The installation is very easy, there is nothing to worry about. Just click on the file that you have downloaded or if the file is in zip format then download winzip to unzip the file then install it.