Once you have purchased software for Windows and you want to install onto a Mac you can do the following as described below.
The first step is to download the software. However, there are a couple of ways to download the software. Use the Autodesk Virtual Agent as per link: https://knowledge.autodesk.com/customer-service/account-management/software-downloads/previous-versions/virtual-agent or use the Trail download from the Autodesk website: http://www.autodesk.co.za/products/autocad-lt/free-trial Just remember the site picked up your operating system you ’ll need to visit the site with your Mac.
The suggested method is to download the software from your Autodesk Account. Do the following: Visit the website: http://manage.autodesk.com log in and click on Management tap at the top. Find your software, in this case its AutoCAD LT and click on the Downloads link. See below.
A dialogue box will appear showing the download options. Click on the “Browser Download” button next to AutoCAD LT for Mac option.
Once downloaded you can install onto your Mac and activate.
If you have any other version for Mac software on your PC you can uninstall it by doing a clean uninstall as shown in the process here: Clean Uninstall of AutoCAD for Mac
Please make sure you use both the serial number and product key from AutoCAD LT for Windows when installing. You can obtain these numbers on the Autodesk User portal http://manage.autodesk.com See below.
In this case the AutoCAD LT 2016 for Windows key was: 057H1 and remember not to use the AutoCAD LT for Mac product key.