You'd have to mannually find all the jars and bring them in. Based on feedback in Seam 2 there were many people wanting Maven integration, so we went with Maven for Seam 3.
it may be more a maven question than a seam question:
what do i have to do with the seam artifacts so maven can use it? Do i have to configure the path to seam3 somewhere?
Did you install maven  ?
If you have maven installed - then you can try running "mvn clean install" in one of the examples folder like "seam-booking" - you can check the corresponding README here : https://github.com/seam/examples/tree/master/booking
jboss dev studio comes along with a maven plugin. A maven repo is created as well.
i'll try your example