Change the style of the web client

Hello , i want to change the css of the web application, i am a developer but not a java expert so if you can plz, can your tell me where can i add the class of my template already exist or a tuto of gwt template who can help me

thanks

Traccar doesn't use GWT. It uses pure JavaScript with ExtJS framework. For ExtJS theming see this:

http://docs.sencha.com/extjs/6.0.1/guides/core_concepts/theming.html

sorry, was on an older version, thank you for the work realized