New Computer Build - Need some help with CCleaner

I've been using CCleaner for quite some time, and purchased a license for CCleaner Pro. Now I'm building a new system since Microsoft dropped support for Windows XP (thanks a heap Microsoft). Upgrading the whole system including Windows 10 OS, new HDDs and SSD.

Once I have the system up and running, how do I get CCleaner back onto the new system? I have already saved my License Key and Reference Number to a USB External HDD. It should be able to be read by the new system via the USB. Can I download the new CCleaner to the external drive today, install to the new system later, and just enter the License info to get it running? Or should I download the new program after I get it running, and install then?

You can should be able to install the free version then enter your info into the register. There's no time limit after the download before you need to register it, so either of your options in the question will result in the same outcome. Hope that helps