Can't insert Liscence key

I have been using avast on all of my pc’s and laptops for about 4 years now. iv just come to put it on an old laptop. Downloaded the free version of avast registerd it and had a liscence KEY sent through. now the only 2 options i have to registter it are inserting an activation CODE or that is in 3 sections of 6 characters. Now the key i have is a long code well more that 18 characters. what can i do to sort this. i tried uninstalling and redownoading it again thinking the paid version may have a different way of registering. apparantly not. Any suggestions?

avast! 7.x: Registering avast! Free Antivirus
https://support.avast.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=1073