To perform multiple comparisons for a Two-Way ANOVA, use General Linear Model. Suppose your response is called A and your factors are B and C.
1. Choose Stat > ANOVA > General Linear Model.
2. In Responses, enter A.
3. In Model, enter B C B*C (to fit the multiplicative model).
4. Click Comparisons.
5. In Terms, enter B C.
6. Check the methods you want.
7. Click OK in each dialog box.