Hello,
There is currently no simple way to do it. We will improve the automation system in the future so this can be done in an easier way.
Currently, you should go in the AcyMailing configuration, tab Queue process and set the "Automated tasks" option to the time you want the automation to be triggered.
Then, you should wait a Sunday to activate your automation (you should do it before the hour you set in the configuration).
This way, when it is the set hour, AcyMailing will trigger the automation and the next trigger date will be set to the Sunday 2 weeks after.
This is not a perfect way, and you can only have one hour set using this solution. But it may help till we improve the automation system.
Best regards