Create a New Weekly Entry with the '+ New' button.

Tag your weekly focus from the 'Areas' dropdown.

After creating your New Week, head over to the 'Today' page.

If you haven't already, create a new entry for Today.

Select your new Weekly entry in the filter, also (e.g. Week 2)

Click anywhere on your 'Today' timeline to add a new task for today, which will also be added to your new Week.

Head back over to your new 'This Week' view.

You should now see any tasks you've added to 'Today' in your Week view. You can now add more tasks to your week on future days.