I currently have Ccleaner Pro on my desktop. I am impressed with its workings and would like to expand it to two laptops we own. Can someone tell me how to do this?
If your current licence is only for one PC then you should contact support and ask for an upgrade.
You can use the form here: https://support.ccleaner.com/s/contact-form?language=en_US&form=general
You can upgrade to Pro Plus which will cover 3 devices, or to Premium which will cover 5 devices. Here are the current standard subscriptions https://www.ccleaner.com/ccleaner/plans
The devices covered can be a mix of Windows, Mac, and Android devices. (But not iPhones currently).
Normally you would buy a new subscription of Pro Plus or Premium for a year, but the time remaining on your current licence would get 'merged' and added on to that so that you don't lose out on what you have already paid for. (In fact you win because that remaining time becomes valid for the multiple devices instead of just one).
There are sometimes other offers (or cheaper prices) that they can give at various times, so it's always worth asking.