It is mentioned in the exercise text. You should enter something as follows: 
    labels 0:s1; 1:s2,s3; 2:; 3:s0,s1,s2;     // encode Q
    labels 0:; 1:s2,s3; 2:; 3:s2;     // encode Qf
    init 0,1;
    transitions (0,{a},,1); (0,{},,2); (1,{},,3); (3,{a},,3); (3,{},,3);
    accept 2,3;
The labels define the sets of states that form the pairs (Q,Qf) of the breakpoint construction.