Our IT department is upgrading us from CS6 to CC. They are in Singapore and we are in Malaysia - so they have sent us a serial number. However, I cannot figure out how to do this with a serial number. Obviously we can download the CC desktop app and

Cloud programs do not use serial numbers... you log in to your paid Cloud account to download & install & activate... you MAY need to log out of the Cloud and restart your computer and log back in to the Cloud for things to work

Cloud Plans https://creative.adobe.com/plans

Download & Install instructions https://forums.adobe.com/thread/2003339 may help

Also go to https://forums.adobe.com/community/creative_cloud/creative_cloud_faq