PaySuite customers have 'Powered by PaySuite' on the Employees page. See screenshot below.
If you don't have PaySuite on your Employees page, view this article.
Once your payroll has been created, it is not possible to change the pay frequency from weekly to monthly, or vice versa. The Pay Frequency field in Payroll Settings will be inactive and not available for change. Before saving you will be prompted to verify if the details entered are correct.
If you need to change frequency mid year, you can create another payroll and manually migrate the data from one payroll to the other.