1. What version of Mathcad are you trying to install?
2. If you have the installer and the license file in the same archive, then you need to unpack the files. And when choosing a license, point to this license file.
3. Also many installation answers can be found here - "All About Mathcad Software Installation": https://community.ptc.com/t5/PTC-Mathcad-Installation/All-About-Mathcad-Software-Installation/m-p/70...
Mathcad 3.0 Student Edition
That url does not have the version I'm looking for.
Do I have to do anything with the license dat file besides saving it to a folder?
If not, both installer and license file are in the same folder. However, when I try to use the installer, it does not detect any application in the application selection tab.
Is it a floating license or a node locked license file? Based on its type you need to decide whether the license manager needs to be installed or not.
You need to install license server for a floating type license file. If possible, please share license file here.