How to Use Containers on a Tableau Dashboard
Step 1:
Start with three sheets. A Bar Chart, Line Chart, and a Map View.

Step 2:
Set your objects to Floating. Drag in a vertical container.

Step 3:
Add any color to the container so it is easier to see. Drag two blank boxes into the container. This will make it easier to add more objects later.

Step 4:
Drag the bar chart and line chart into the container. If you are still using floating objects, you can either hold the control key down, or change it to tiled.