In your account page, scroll down the page to your product, do you not see a download button on the left. Click on that and it should take you to another page (Steps to install your new purchase) This is printed at top of page (Find the product/s that you purchased below, then click the Get (Product Name) to download your the installation file for each product you purchased. Select Save File, then when it has finished downloading, click on Open File to start the installation.
NOTE: These Versions all Run under Windows 10, 8.1, 8, and 7.
If your versions are older they may not run on windows 10 and you may need to purchase upgrades.
You can download all the installation files but they will not install until you
un-install your previous versions while on line to free up your registration.
If you have any problems registering any product you will have to put in a support ticket asking for registration reset.
The Help page is here:
http://help.mtu.com/support/home
With links to Support ticket, it also shows phone # which is worth a try.