First you need to have a coupled return. Then add a T3 slip to your return, you can choose to enter 50% as your claim percentage for the T3 slip;
Second, select this T3 slip, choose menu "Slips | Share Tax Slip with Spouse"
3. After sharing the T3 tax slip, you will see a new T3 slip in spouse's return, and the shared slip name changed to "S - T3 - xxxx".