For the host
The host has screen sharing capability. On the bottom left of the video section, the host can find this icon to share his/her screen.
By default, all participants do not have screen sharing capability. The host needs to grant permission to specific participants.
It can be done inside "Participants and groups"
And toggle on the "Screen share" for a specific participant.
Once permission is granted, the participant should see this icon on the bottom left of the video section.