As an admin, you will need first to ensure the feature is enabled into your videocall Flow. To check that, head to the main flow page list here.
Once there, either create a new flow or select an existing one.
Once on the flow builder, look for the 'Configuration' tab and make sure the Pointer feature is enabled.
The feature will allow agents to point at portion of the customer video or screen but not vice versa, meaning that customers won't have the same option in the interface.
As an agent, when you join a call where the feature is enabled, hover the mouse on the customer's video and click on the dedicated icon on the top right as shown on the screenshot below.
Once enabled, hover the mouse on customer's video so that they will see the pointer too.