How is heat transferred through convention?

When one delegate at a convention abuses another the second may retaliate. If their supporters then take up the exchange of abuse, heated arguments will spread. That is one way in which heat is transferred through a convention.

However, if you meant convection, then you are talking about the transfer of heat in a fluid. A part of the substance gets heated and due to thermal expansion becomes lighter. It therefore moves away, allowing cooler bits of the substances to move next to the heat source. As that part gets heated it moves away, and is replaced by yet another cooler part. Convection cycles are set up and these allow heat to be spread across the substance.