I recently signed up to be a pro DM, and I'm using the character builder on D&D Beyond for my players and Encounter Builder for encounters. I was wondering if there was a way for some player who are beginners if I can build their character in my Campaign and then assign it to them? Or do they have to build it under their own DDB Account and then join my campaign? Is that the only way it can be done?

The reason I'm wondering is, for beginners it would be a lot easier if I could screenshare with them showing them as I build their character vs. having them build the character on their own and have to have them screenshare with me or just describe to me what they are doing...

Yes - you can go into your Campaign, "Create Unassigned Character," to go through the creation process (presumably with the new player on a screenshare or stream), and then assign it to said player afterward if they are in that campaign.

Awesome, thank you!