To register your IDM license, follow these steps:

1. Open IDM and go to the Registration tab.
2. Click on Registration again in the dropdown.
3. In the popup window, enter your first name, last name, email address, and the serial number (license key) you received upon purchase.
4. Click OK. Your IDM will be successfully registered, and you’ll see “Full Version” under Help > About IDM.

For detailed process you can read article How to register IDM with my serial number

If you see a warning message about using IDM on other computers when you try to install it on a new computer, you need to uninstall it from all those computers if it is possible. If you are sure that IDM is not installed or will not be used on any of those computers again you can just ignore this message and continue registration. Otherwise, IDM will detect that it is being used on several computers and your serial number will be blocked.

If you want to move IDM on another computer, you need to uninstall IDM from the old computer first if it is possible. If the old computer is broken, stolen or formatted it is also OK. Then you may install and register IDM on a new computer.

Please note that IDM has per computer license. In order to use IDM on several computers at the same time please obtain licenses for each one.

If you often reinstall your system on the same computer, please download and install the latest version of IDM. It has additional binding to the hardware and will not block your serial number if you use it on one computer. Also, it is always better to use the same computer name after each reinstall.