first u should know the rocks of Dominoes it has all combination between the seven numbers

0-0,0-1,0-2,0-3,...

since the repetition is occurred u will have loops for example u have a rock with 0-0 so 0 is joint with it self same thing for all the vertices and every vertex is joined to all the other ones since all combination found

if u find the Euler cycle u are done since Eulerian cylce pass through all edges without repetition, and u want to order the Dominoes in a cycle

there is a theorem that said if all vertices in the graph has an even degree then the graph is Eulerian so it has a cycle that pass through all edges once

the graph will look like this