how do I add imessage and facetime to Icloud.com or Icloud app?

You don't. They are part of the iCloud service suite, but FaceTime and iMessages use separate distinct applications, not the iCloud.com web site.

If you're on Windows, then things are a little trickier. You cannot initiate a FaceTime call on Windows, but you can join an existing call - but the host has to send you a FaceTime chat link (which they can do within the FaceTime app on Mac or iOS). The link opens a web-based connection to the FaceTime call:

Join a FaceTime call from an Android or Windows device - Apple Support

For iMessage on Windows, there is no option.