Per IRS Publication 915, Social Security and Equivalent Railroad Retirement Benefits, page 6:

Canadian or German social security benefits paid to U.S. residents.

Under income tax treaties with Canada and Germany, social security benefits paid by those countries to U.S. residents are treated for U.S. income tax purposes as if they were paid under the social security legislation of the United States. If you receive social security benefits from Canada or Germany, include them on line 1 of Worksheet 1, in Publication 915.

Therefore, you will enter these benefits into the TaxAct program as if you had received them from the U.S.

The portion of the benefits that are taxable will depend on your total income. If your total income is above certain limits, a maximum of 85% of your benefits will be subject to U.S. tax. 

To enter Social Security Benefits in your TaxAct program:

1. From within your TaxAct return (Online or Desktop), click Federal. On smaller devices, click the menu icon in the upper left-hand corner, then select Federal
2. Click Social Security Benefits
3. The program will proceed with the interview questions for you to enter or review the appropriate information

For additional information, please refer to IRS Publication 901 U.S. Tax Treaties.