Rune reading, lot casting, whatever name you call it (as there are many names to call it) it can be very complex and time lengthy to interpret the runes.
Any ways. So to cast and read the runes for a person over distance or a person you meet online you can really do it the same as you would as if the person were in front of you. If you know what the person looks like it can better help you focus on that person when divining. But in the event that you don't, use what information that you can like a username or a profile picture (not of the actual person) as a catalyst of a sort to focus on the individual for casting the lots and reading runes. It may not be as good as if the person was physically known to you, but works.