Qo = input state, Q6 -- final state
Qo--Q1 using 'a'
Qo -- deadlock using 'b'
Q1 --- Q2 using 'a'
Q1--Q6 using 'b'
Q2 -- Q3 using 'a'
Q2 -- Q5 using 'b'
Q3 -- Q4 using 'b'
Q4 -- Q5 using 'b'
Q5 -- Q6 using 'b'
Follow above step plot the diagram you get 8 state ( Qo to Q6 and deadlock state )
complete the each state for each and every input alphabet i.e. definition of DFA
Still any confusion comment below !!