How do I change it from MOTD?

Use #webpage-title in your configuration.txt and remove the #.

webpage-title : this setting, a string, is used to specify the title for the Dynmap maps web page. If not specified, it will attempt to use the 'server-name' property from server.properties. If that is undefined or set to 'Unknown Server', the title will default to 'Minecraft Dynamic Map'.

Reference: Wiki: Base-Plugin-Settings