License for 3 computers - need to drop one and put on another computer

Peter,  Please refrain from carrying out multiple postings on the same subject! You won't obtain an answer to your query any faster!. See other posting (https://support.avg.com/answers?id=906b0000000LRUCAA4).
AVG Guru

I have 2 computers at home. The third license is on my granddaughter's computer which she doesn't use. I'd like to remove the license from that computer and put it on a new computer at my home. I tried adding the license number but the computer won't accept it. How do I do this? Thanks.

Peter,  Please refrain from carrying out multiple postings on the same subject! You won't obtain an answer to your query any faster!. See other posting (https://support.avg.com/answers?id=906b0000000LRUCAA4).
AVG Guru